Best-Laid Plans: The actual Keys of The Scarlet Keys

I’ve been asked if i could put up a visual spoiler of the Keys from the Scarlet Keys up on my site, so … well, here it is. To put some more meat on this page, i also went and commented on how useful their Stable side is, how difficult it is to flip back to Stable and how difficult it is to actually acquire in the first place.

Stable: This key is super useful for rogues and other investigators with low willpower and/or agility that struggle with treachery tests. When i use this key, it’s usually to discard something like a Frozen in Fear or deflect a Rotting Remains. Super worth it.
Unstable: If you use this key the same way i do, the key basically allows you trading one encounter card for another. That seems like a fair trade to me in most cases. If this is in enemy hand, this key is a menace though.
Acquisition: All you need to do is finish Riddles and Rain without wiping out. Easy enough.

Stable: Useful, but not extraordinarily powerful when used fairly, but in some situations that come up in the campaign, this almost lets you skip certain challenges. Without going deeper into spoilers, the Sable Glass lets you trivialize much of the final scenario. Gets better with more players since that makes it more likely that mini-cards stack up in one location and the Sable Glass can help you get a handle on that.
Unstable: In low player counts, this is barely a cost but with more players this becomes a bit more annoying to set up as someone will usually mind having their highest cost card taken away. Still fine though, this isn’t a key that needs to be flipped back and forth a lot. If this ends up on a coterie member that can trigger it often, this key can become trouble.
Acquisition: Rather difficult to get, as you need to either need to do very well in On Thin Ice or defeat Thorne if you have not done that well… and they are maybe the most terrifying enemy in the whole campaign (at least on their own merits… Tzu San with her key is a special kind of BS). Note that if you do ally with Thorne, they will show up with the key in hand for the finale, so you do get to abuse the crap out of the Sable Glass then anyways.

Stable: Quite powerful. Both parts of the effect are great, moving enemies around and getting free attacks can both be useful and if you can profit from both at the same time, you get great value here.
Unstable: Flipping the card back scales very heavily with player count, while the Stable side doesn’t (or at least only very little). That makes this a tough sell to flip to Stable if you can avoid it. Another one you really don’t want to see on enemies.
Acquisition: Well, i didn’t manage to beat Shades of Suffering yet. Maybe some day.

Stable: Pretty great, as it doesn’t just give you -3 cost, but also an extra action. Fantastic key to have for your first setup turn, even if you never plan on flipping it back.
Unstable: That being said, it’s often reasonable to actually do use that Shift back to Stable. I consider this to be less restrictive than Sable Glass to stabilize… but worse in enemy hand because getting hit by it multiple times will just rip apart everyone’s hand.
Acquisition: You need to go against the Claret Knight and take the thing from him. Doing so requires some firepower but isn’t particularly hard (compared to what else the campaign has to offer). You can do so relatively early in the campaign too.

Stable: A free clue. Sure. Always useful, but rarely something to get excited about. You can use this key to expose a mini-card at your location as a free action, which seems more interesting to me than just a free Working a Hunch. One of the limited ways to expose a mini-card at a connecting location which is super useful in several circumstances.
Unstable: Can be set up to work well, but again the Unstable side scales with player count when the Stable side doesn’t. If you end up with assets that ran out of charges (or that have doom on it) this can even end up being useful, but most of the time it’s not worth flipping. ABSOLUTELY HORRIFYING on enemies that can trigger it repeatedly, most of all its natural owner, La Chica Roja.
Acquisition: Win the race for 3 targets against notCarmen notSantiago. Making it to the “secret” second part of the scenario is not required, so this key is reasonably easy to grab.

Stable: Highly dependent on what you have to add uses to. Putting another piece of ammo or a charge on a spell is usually not terribly exciting, but i could see this being solid if you have something like a Fingerprint Kit(4) or a level 5 spell to feed.
Unstable: Again, scales with player count, the other side doesn’t. Considering that the usefulness of the Stable side is already dodgy, this will almost never be worth shifting yourself. In enemy hands it’s super unfun, but at least it’s not The Weeping Lady.
Acquisition: No fighting necessary, just get on Tuwile Masai’s good side. To do so, you need to not betray the coterie (too much) and possibly follow the guy around from Nairobi to Bermuda. If it’s reasonably on your way, might as well pick it up but i’d argue this is the weakest of the keys.

Stable: Great emergency button to press and notably it’s not restricted to non-Elite which is huuuuuge in this campaign. Worst case, it exposes a mini-card without taking an action.
Unstable: A point of horror for everyone is a small price to pay if this alone keeps Amaranth and her pet zombie lion from attacking every other turn. Obviously this cost can still be problematic, but depending on the circumstances it can absolutely be worth it. On an enemy, this provides a rather strict clock that will force you to deal with it as soon as possible.
Acquisition: Again, just requires some travelling, you’ll get it from Dr. Irawan when you follow her from Rio to Manokwari. There are some time requirements to this one, which makes it a bit more awkward to get than the Bale Engine, but then again it’s also much more worth getting.

Stable: Amazing for wiping away trauma for the whole team on turn 1. Even if you never end up using it a second time, that alone is so very powerful.
Unstable: How strict exactly we are to interpret this ability is apparently still up for debate, but current provisional ruling has been that it only requires one enemy with damage on it to be able to shift back (a stricter read would be that EVERY enemy in play needs damage on it that can be healed). This is not a huge cost, in fact i found that i often would need to specifically set it up so that i don’t just kill things immediately if i want to flip this back. On an enemy, this makes quite the impression in its original scenario (Dead Heat) but is rather tame if it appear later on.
Acquisition: You gotta rip it out of Amaranth’s head. While very satisfying to do, this is not an easy task. But if you have the firepower, it’s very much worth doing.

Stable: Dealing 1 to multiple enemies is pretty much never worth doing, but 2 testless damage to one target, no questions asked? That is spectacularly useful for fighters and non-fighters alike. Again, this can be used to expose a mini-card without an action, but you will likely have better uses for it available.
Unstable: Worth the cost for shifting it. I consistently find this to be one of the most useful keys and getting more uses out of it is great. Of course you need some healing if you really want to go deep on this, but even if you just shift it back once or twice, you get to snipe two or three enemies with it.
Acquisition: Desidorio has this one and he is a bit extra about it. Not only do you need to finish Havana, you also need to spend some time durdling around in the area before you can grab it from his safehouse. Not difficult, just annoying and can be hard to fit into your travel schedule.

Stable: Card draw and card selection, that’s always useful. I like this particularly during the early setup where it gives more options, almost as if you get another mulligan to try and get your most important cards. But of course this effect is just consistently useful, no matter when you use it.
Unstable: Doom mechanics are scary, but when you have control over it, then you can get some great opportunities to bypass the drawback. Whenever you want to get rid of an asset anyways or when you are about to take out an enemy or discard a treachery at your location, you can also get a key shift out of it for near no cost. That being said, if an enemy has it, it quickly gets less pleasant…
Acquisition: Either betray Ece or just do Istanbul without her and the key is yours. Not too difficult, not too easy, perfectly reasonable.

(Disclaimer: I don’t own Fortune and Folly yet, so i didn’t have opportunity to play with this key myself. Also i can’t make proper scans of them, so these two images will have to do for now…)

Stable: Seems fine. Gives better chances at a single test, but doesn’t guarantee it and especially in Scarlet Keys the chaos bag is rough enough that i probably would rather have a solid skill bonus than just a redraw. Still, some investigators and player cards do care about specific tokens and those could get good mileage out of this ability at important points.
Unstable: On the other hand, the Wellspring is quite easy to flip back and this doesn’t even scale with number of investigators like so many others. You often run into tests that you either don’t care about or are going to fail either way. Worst case, you can just take an action to investigate and trigger the Shift on that. In an enemy’s hand, this can potentially be annoying and cost important tests. However, since it is limited to a test in the same round and many Coterie enemies trigger their keys in the enemy phase, this often will do nothing.
Acquisition: You get it in Fortune and Folly, the Scarlet Key related scenario that is released as a standalone. I don’t own it yet, i have not played it yet and i have not spoiled myself yet on any of the things happening in it. So no idea how easy this key is to get.

Best-Laid Plans

This page is part of my “Best-Laid Plans” series of campaign Deep Dives. For Scarlet Keys, i had to break it up into parts due to sheer volume. Find the rest of the Deep Dive and other articles about this campaign at my Scarlet Keys hub.

Scarlet Sorcery

Set Size4
Number of unique Cards2
RoleKey manipulation
Threat LevelHigh
# of scenarios4
Appears in: Dead Heat, Dogs of War (all versions), Shades of Suffering, Congress of the Keys (v1)

My take on this set: This set gives some more play to the keys, both on side of the enemies and the players. Key Charge is particularly nasty and one of the very few Surge cards in The Scarlet Keys. Thankfully Surge is not a huge part of this campaign at all, but this one card does pack a punch for sure. Bound in Red meanwhile makes the strongest enemy even stronger and turns them into a real pain to fight head on. By giving the players the option to depower the enemy back to normal by using up one of their own key charges, Bound in Red does manage to give a tough choice that i find interesting to think about. It’s one of those rare cards where the choice isn’t always all that obvious and i appreciate that a lot.
I frequently groan when drawing these cards because they are a pain to deal with, but that’s not necessarily a bad thing. It just means this is an impactful encounter set that does leave a mark on its deck. It also interacts with various other cards in interesting ways. I like it, but it’s probably not a coincidence that the two scenarios that are generally regarded as the most difficult of this campaign (Dead Heat and Shades) both have this set in it.

Number in the encounter deck: 2

What it does: Bound in Red attaches to the Coterie member with the highest printed health and increases their fight, evade, damage and horror values by one. To get rid of Bound in Red, an investigator at any location can take an action and shift one of their keys from Stable to Unstable.

My take: Very often, the coterie member with the highest printed health is going to be one of the unique enemies, like the Beast in Crimson and Amaranth in their respective scenarios or one of the people you “haven’t seen the last of”.
Discarding the card is easy to do in principle since it doesn’t require a test, however it does require flipping a key which will vary in how much of a cost that is depending on whether you were planning on using it and/or how easy it is to flip back. It’s also an action, so it can trigger an attack of opportunity which would include the extra damage/horror from Bound in Red if the investigator is engaged to that enemy.
Since most of the unique enemies tend to have rather high fight/evade values, the +1 from this card only makes matter worse. As a result, this is usually a card that you can’t ignore and spending that action should be done early if the enemy is still concealed.
This card is particularly nasty in Dogs of War version 1, where it will bring up the Beast’s damage and horror to 3 each, enough to defeat a Key Locus on two players in one strike when the Beast patrols into its location.

Threat level: Mid to High. Sometimes not an immediate threat and it does come with a way to discard it. But it’s impactful and hard to ignore.

Dealing with it: The earlier you get this out of the way, the better. Unless the card happens to attach to a regular enemy that goes down in one hit, having this attached to something you intend on fighting can be a real issue. If your group only has one or two keys, the cost of having to spend one of them can sting, especially if you already used them. For example, if all you have is the Eye of Ravens and you used it earlier to pass some other treachery test, you’d have to first turn that back to Stable (which will draw an encounter card, basically giving this Surge) and then spend the key again. Obviously that’s a rather grim effect and at that point, just pushing through the extra fight/evade might become worth the effort. Meanwhile a team that has multiple keys and maybe even doesn’t necessarily need them or is easily able to switch them back and forth will find this treachery easy.

Number in the encounter deck: 2

What it does: Key Charge makes each Coterie enemy use their keys, if available. The card surges, so this happens in addition to another encounter card.

My take: Another high variance card that will depend a lot on circumstances. Since it’s a Surge card that you just get as an addon to whatever regular card you are drawing, you aren’t ever going to be happy to see this treachery, but the actual effect can be all sorts of nasty things like having to draw another encounter card (effectively turning this into Overzealous… yikes) or having to discard random cards from hand or play. For the most part, these effects are going to hit everyone at the table, too.
If your luck is really rotten, then you will draw this with multiple enemy keys on the board. That is going to hurt, no matter what.

Threat level: High. A surge card with potentially high impact.

Dealing with it: Interacting with the card itself is sort of difficult and usually you’ll just have to weather the effects of the key(s) when it happens. As a Surge card, it even is awkward to cancel with cards like Ward of Protection as the Surge will still happen.
This card hurts most when you are already behind, when you had to concede keys to your enemies and might run into the possibility that you have two enemy keys on the board: One from whoever is the unique enemy of the scenario and one from a coterie member you “haven’t seen the last of”. As a result, that extra coterie member should be a priority to take out whenever Key Charge is part of the encounter deck just to take the key off the board. Of course, that’s not going to be easy to do with the key of the scenario specific enemy… after all defeating that one usually ends the scenario itself.

Spreading Corruption

Set Size6
Number of unique Cards3
RoleAction Tax, Doom
Threat LevelHigh
# of scenarios5
Appears in: Dead Heat, Dogs of War (all versions), Shades of Suffering, Without a Trace, Congress of the Keys (all versions)

My take on this set: This set puts the “Suffering” into “Shades of Suffering”. It has high impact throughout all of its cards and attacks from an angle that every investigator is vulnerable to: The action economy. Spreading Corruption is a big part of why Dead Heat and Shades are so difficult to deal with, as those are both scenarios where the players are required to get a lot of stuff done against a tight doom clock without much of a setup period. Randomly losing a couple actions or even turns can quickly become devastating under that sort of pressure. Oh, and those two scenarios have Frozen in Fear as well, which just stacks up in a ghastly way with the two curses from this set. Spreading Corruption is a bit milder in the other three scenarios, but still ranks among the more awful things you can draw from the encounter deck.
That being said, this set is well designed and puts new and fun spins on basic effects that we have seen before. All three of these offer ways to play around them and are just interesting. My only gripe with this set is that this should never be in the same encounter deck as Striking Fear because… ugh. And certainly not three times in one campaign! Have some mercy, MJ.

Number in the encounter deck: 2

What it does: Compulsion enters the player’s threat area and stays there until it is discarded through a double action. While active, it doesn’t do anything … however, the player needs to draw a token from the bag each turn and on skull, cultist, tablet or Elder Thing they must activate the double action at the start of their turn.

My take: This is the rare card that actually made me laugh out loud when i saw it the first time. In spite of the slightly hilarious way how it works, it is a treachery that will cost two actions to deal with which isn’t great. If you are forced to activate this while engaged with an enemy or while required to do something important, this card can really screw up your plans in a painful way. You might not always be forced to use this double action all the time, but you will want to do so as early as possible anyways. Because when you are staring down Amaranth, the Beast or are trying to banish some Geist, this is going to be just awful.

Threat level: Mid to High. It’s two actions to discard without a test, so you know what you get. But there’s also only few ways around it and the timing will often bite you and provoke and Attack of Opportunity to add some injury to your insult.

Dealing with it: This whole set is a great reason to include Alter Fate in your Survivor decklists. Depending on how you are able to handle Distorted Reasoning and Touch of the Beyond, Compulsion can easily be the worst out of the three for you.
Don’t fall for the trap of letting this stay on the table for longer than absolutely necessary. Alter Fate aside you *are* going to lose two actions to it, do it while you are still somewhat in the clear.

Number in the encounter deck: 2

What it does: While Distorted Reasoning is in your threat area, you are no longer able to use the same type of action twice in a row. At the end of each of your turns, you get one chance to discard this curse by passing a willpower test.

My take: Ah, there’s the obligatory treachery with Frozen in Fear’s dreadful timing for discarding it. Can’t make it too easy for those rogues with their 1 and 2 willpower, am i right? Personal trauma aside, this is a great effect for a treachery. It is quite impactful though. At its most basic, it stops you from attacking or investigating twice in a row, limiting how good you are at your primary job. It can also stop you from moving around efficiently, something you will feel especially hard in Shades of Suffering and Without a Trace.
This card does require a bit more attention to detail as usual, as you will need to keep close track of what type of actions you are performing. Especially the “Activate” action can trip you up here. As an example, after using Shrivelling to fight you obviously aren’t allowed to use a Spectral Razor as both would be fighting. However, you also wouldn’t be able to discard Compulsion after using Shrivelling, because both are of type “Activate”. Another example, you would be able to play Shortcut(0) after taking a move action because Shortcut is fast, so it doesn’t count as a an action and also it doesn’t have a bold Move designator. You wouldn’t be allowed to play Astral Travel or activate Sled Dogs afterwards though, as both of them do have the Move designator and count as an action.
Oh, also here’s a “fun fact”: Shades, Dead Heat and Congress of Keys all have both this set and Striking Fear, so if you don’t have at least 3 willpower you better get used to being tied down by Frozen in Fear, Distorted Reasoning, Compulsion or any combination of the three.

Threat level: High. If you aren’t able to pass that willpower test, this will severely hinder you from taking your actions in an efficient manner.

Dealing with it: Well, the line of treacheries with this particular timing for their willpower test are notoriously hard to get rid of for some investigators. And even if you hold an answer like Alter Fate or Logical Reasoning (this is a Terror… being able to discard Distorted Reasoning with Logical Reasoning makes me unreasonably happy) you might be tempted to hold onto that for Frozen in Fear. At least you can play around this card somewhat. Worst case, you’ll have to weave in a resource or draw action inbetween your investigations and moves or an evade between your fights.

Number in the encounter deck: 2

What it does: Touch of the Beyond places a doom token on your most expensive asset. If you have no valid targets, it surges.

My take: As far as variants on Ancient Evils go, this isn’t the worst. It doesn’t advance the agenda as part of its effect, so if you draw it during the “Witching Hour” (the turn before you’d advance anyways) it’s basically free. If the doom is put on an asset that you might want to get rid of before the doom threshold is met, you also get off easy.
That being said, it is still a doom effect that comes bundled with other high impact treacheries that are already slowing you down and in scenarios that are already among the more difficult ones. It’s a weaker Ancient Evils, but you still won’t be happy to see this most of the time.
As a rules note, as far as i am aware an asset with cost “-” can not be considered highest (or lowest) cost because it simply doesn’t have a cost. So if all you have in play while drawing it is a couple Permanent cards (Charisma, Charon’s Obol, Short Supply, etc) then those won’t be getting a doom and Touch of the Beyond will surge instead. Let’s all be thankful for the little things.

Threat level: High. There’s some scenarios with nasty doom clocks using this set, so this card is high impact.

Dealing with it: If you are playing high cost assets with limited charges, you might be in luck and be able to get rid of the offending asset without it costing you much. Otherwise you might have to decide if for example overwriting your doomed asset with a fresh one from your hand is worth it. In Without a Trace and Congress of the Keys, you might even be able to use the asset with the doom token as a hollow when forced to sacrifice something.
Finally, there are of course a couple cards in the Mystic card pool that remove doom or mask it from the agenda threshold. Touch of the Beyond isn’t enough of a reason to play those cards, but if you are already doing so for other reasons, you certainly are well equipped to safely defuse this treachery in many cases.

Dealings in the Dark

Encounter sets in this scenario: Dark Veiling, Agents of Yuggoth, Ancient Evils, Dark Cult, Locked Doors, Midnight Masks Treacheries
Available experience: 5 (locations) + 1 (Umbral Harbinger) +1 (Emissary of Yuggoth) = 7XP

Location: Istanbul/Constantinople
Involved Coterie Members and Keys: Ece Şahin, The Twisted Antiprism
Time spent: 3 or 2 time, depending on whether you have Ece accompany you or not
Nearest other scenarios: Alexandria (1 time), Marrakesh, Tunguska (2 time)

Size of the Encounter Deck33
# Enemies8
# Willpower2
# Agility4
# Doom14
# Damage7
# Horror6
# Concealment12
# Hollow0
Note: The cultists in this scenario collect clues instead of the usual doom. I still counted them under the Doom category here because the purpose is much the same: Provide a timer to race against.

Synopsis: The investigators arrive in Istanbul (formerly known as Constantinople) and meet with Red Coterie member Ece Şahin, who asks the team to help her find The Twisted Antiprism before more sinister forces do. The group can either accept, deny or deceive her. Whatever the choice, the scenario itself plays out the same, as a race for clues between the players and the opposing cult. There’s three distinct parts to Dealings in the Dark: First just a few locations around the Hagia Sophia are available. Then, the search leads towards the Great Bazaar. Finally, with the Key found by either faction, the cultists and the players try to secure the key by bringing it to the docks of Galata.
If successful (depending on their initial choice on how to treat Ece), the players then hand over the key to Ece or keep it for themselves. They also either make an ally out of Ece or not.

My take on this scenario: This is a brilliant scenario driven by great mechanical interactions. Alongside Sanguine Shadows, it’s the one most heavy on concealment, but it uses it in an interesting way to shield the otherwise comparatively fragile cultists from the players. There are basically two timers, with the cultist clue count taking the role of what the doom timer usually does. Meanwhile, doom takes a backseat while still being relevant because it spawns more waves of cultists. The result is a scenario that for most of it similar to Carcosa’s Echoes of the Past, but working much better in terms of creating urgency and making the cultists a credible threat. The third act can get quite mad, with the key changing hands until one faction finally gets out of the city with it.
This is a scenario that feels very long and exhausting to play due to how much is going on. I don’t mean that as a bad thing, but after playing Dealings i am definitely ready for a break in a way that i usually only get from The Secret Name…
This is easily my favorite scenario from the Scarlet Keys, i enjoy it both for the relentless pacing and the unique structure. If i had to make a complaint, it would be about how this scenario isn’t really able to be done with evasion based character as enemy handler. The ability to “evade clues away” from cultists is mostly a trap, you really need to be able to defeat these guys. Of course it’s nothing new that evasion is weak against cultists because it doesn’t do anything against their doom, but the way this scenario spawns wave after wave of them means that even someone like Tony or Mark is going to have to work overtime to wipe all of them from the board. Most unfortunate though is that Kymani, who is actually a TSK investigator, gets hardcountered here. The cultists go back into the shadows after being evaded, so Kymani never gets an opportunity to use their double evade to defeat thing.

Scenario specific encounter sets: Aside from the usual locations, acts etc., the Dealings in the Dark set adds four different cards that are shuffled into the encounter deck. One of them, Shadowed, is actually a reprint from The Forgotten Age, where it already was a quite potent card that combines doom, horror and surge to a package that one is never happy to see. In this scenario, it also gets a damage counterpart in Accosted. Light Out of Void piles on even further, adding more doom, damage and/or horror. Each of those treacheries gets 2 copies. Finally an enemy is added to the deck with 3 copies. The Sinister Aspirant collects a doom every turn, similar to Wizard of the Order (although with different timing) and brings a relevant 3 health to the table, making him less trivial to wipe from the table as most other cultists.

Chaos Tokens: In comparison to some of the nonsense this campaign gets up to, the chaos bag is actually almost tame in this one. Still, that’s only when compared to the rest, this is not an easy bag at all. The skulls scale with the amount of tokens on cultists, capped to -3 (-4 on Hard/Expert). Tablets are pretty rough, with a -3 (-4) and if you fail you have to place one of your clues back on your location. Elder Things are only -2 in all difficulties. On Easy and Standard, failing a test with an ET will add a doom to the nearest Cultist. One Hard and Expert, it will add the doom no matter the outcome. This is a massive ramp up from E/S to H/E. On E/S i would prefer having ET in the bag, but on H/E the tablets seem a bit milder. Finally, the cultist tokens that are added over the course of the campaign are -5(-7), but can be brought down to -1(-3) by putting a doom on a cultist. That is actually fine by itself (at least on E/S), but will potentially stack up with the Elder Thing. In theory there could be 7 tokens in the bag that all add doom to cultists…

Act/Agenda: The scenario is divided into three parts and this is reflected in the act deck, of course. Act 1 covers the hunt for the first 4 clues per investigator, among the initial four locations. When advancing from act 1 to act 2, the two big set aside enemies enter the deck and all players and enemies are moved over to the bazaar, a separate set of six locations. During act 2, the players will have to bring their total clue count up to 8 per investigator. No additional abilities are mentioned on the act cards, but a separate story card handles how doom added to cultists is added as clues instead and how they can collect permanent clues when more than 3 clues are on one enemy. During these first two acts, only one agenda card is active, with a small doom threshold of 4. When met, new cultists will spawn or the cultists will outright gain clues to their story card. Each time the agenda flips, it will trigger an additional time, severely ramping up over the course of the game.
For act 3, the previous act and agenda cards are removed and replaced by a single card, “The Chase”. During the chase, the story card is also flipped to its other side with a new ruleset for moving cultists and them trying to steal the key away from the investigators and fleeing with it. Like agenda 1, the chase resets itself when its threshold is met and increases the pressure on the investigators.

Ece Şahin: This coterie member is on our side for once. During setup, Ece asks for our help in retrieving the Twisted Antiprism and we have the choice of either promising her our help, deceiving her or outright telling her that we will want the key for ourselves. In either of the first two choices, Ece will start in play under an investigator’s control. She is quite powerful, with a significant amount of health and an ability that basically draws an extra card per turn as long as you have keys to shift.

The Umbral Harbinger: This is one of two victory enemies in the encounter deck (the other one being the Emissary of Yuggoth) and the only enemy without Concealed. With 5 health it takes a couple of actions to take out, but its most important ability is putting doom on cultists whenever its being hurt. This will usually result in two or three additional doom tokens. It has low agility, so evading it is an option especially if you are already in act 3. Of course, doing so will forfeit the victory point…

The Cultists: There is seven cultists in the deck. While that doesn’t seem like very many, the scenario also has Mysterious Chanting to fetch them up, several cards that cycle when no cultist is around and of course the recurring effect from the agenda that finds more. So these will constantly enter play and the players will want to stay on top of this threat, defeating these enemies whenever they pop up. Instead of doom they collect clues in this scenario, but ultimately that’s still very similar in that it’s a counter for the players to race against.
The scenario offers players the ability to evade cultists to steal one of their clues, however doing so will return that cultist to the shadows. However, that ability is a bit of a trap. You end up spending many actions on exposing and evading an enemy for just 1 clue which you could’ve gotten easier from a location. And after that you still have that cultist running around which will gather more clues or come after you in the final act.

Treacheries: This is a scenario with Ancient Evils in it, but thankfully it doesn’t (directly) stack up with the cultists. There’s also no reshuffling of the encounter deck, so Evils is rather tame in this. It still does move you towards more waves of cultists, of course.
The encounter deck has quite a bit of damage and horror in it, mostly from the three scenario specific treacheries, but also from Hunting Shadow which is often a difficult choice to make. Of note, the four initial locations have 4i clues among them, the exact number required to advance the act. If you spend a clue on Hunting Shadows, you will need to make up for it either through the ability on the Hagia Sophia or through evading cultists. While we are on the topic of the Midnight Masks treacheries, False Lead is an absolute pain in this scenario and can set you back severely, especially when you have to drop 3 to 4 clues on a shroud 5 or on a Locked Door. I’d argue that the two treacheries from Masks have never been more impactful than in this scenario.
Aside from the doom/clue shenanigans, Dealings of the Dark is of course dominated by the concealment mechanism. Both cards from Dark Veiling are basically just more sources of damage and horror for the pile. Tenebrous Eclipse is more interesting, stopping you from exposing more cards after your first. This is usually only relevant after exposing a decoy, but this scenario has enough enemies in the shadows at the same time that it can matter.

Locations: There’s a lot of locations in this one, at least for a Scarlet Keys scenario. It starts out harmless enough with 4 locations for the initial act. For the second act, another 6 (out of seven possible ones) is added. And for the final act, yet another location comes into play. Since you have to go through all of the bazaar and then also back again, you are going to travel quite a bit in this scenario, making cards like Pathfinder or Sled Dogs very valuable. Of special note is the Hagia Sophia which has the capability of giving you more clues in case you had to give some up to treacheries. This becomes very difficult very fast though. While the first clues are easy to pick up at difficulty 2, the next ones are at 5. And then 8, 11, etc. Realistically, getting more than 2 clues per investigator out of the location will require testless ways like Drawn to the Flame, The Weeping Lady key or Grete Wagner.

Reward and Failure: Depending on how you answered Ece Şahin’s request, your rewards are a bit different. If you decided to help her, the Twisted Antiprism will go to her but you will secure her help for the finale (both the vote and the scenario itself). She’s a rather good ally and she will of course bring her key to the finale as well, so that’s definitely worth considering. Taking this route will make the scenario take 3 time.
If you deceive her, you will steal her key after she helped you in this scenario. In that case she still won’t vote against you in the finale, but she will abstain. Again, this makes the scenario take 3 time.
If you outright refuse her offer, you go into the scenario alone, but are of course able to keep the key for yourself if you succeed. Ece will still vote in your favor this way. Also, the scenario will only take 2 time because you can embark straight after fleeing the Galata docks without having to meet up with Ece first. So this version let’s players sort of have the best of each world, but it will mean that they have to play Dealings without Ece’s support which can be tricky early on.

The Twisted Antiprism is one of the better keys, offering card filtering and draw that is super useful during setup. Shifting it back to Stable requires putting a doom on one of your cards, which can often be done without repercussions if you have assets that you want to get rid of anyways. You can put the doom on an encounter card at your location as well, so if you are about to defeat an enemy or discard a treachery from your threat area, you can get a free flip to Stable out of it, too.
This is also one of the very few scenarios that offers a reasonably high XP payout of up to 7. Getting all of these can be tricky, though. Two VP are hidden inside the encounter deck and you have to find them first. One of the bazaar locations is removed from the game at random, this might bring your possible total down to 6. Finally, the Galata Docks can be very awkward to clear because at that point you are likely already fighting tooth and nail to get out of the scenario. Clearing a 5 shroud location might not be in the cards for you then. Keeping a Drawn to the Flame or Intel Report in your backpocket for that can be a good idea.
Thanks to the decent XP, a useful key, possible support by a powerful ally and the lack of a highpowered coterie enemy, Istanbul makes for a great first scenario after Riddles and Rain.