Secret War

My take on this set: This set is mostly notable to me for Secrets Lost. Most campaigns do have some sort of treachery that potentially discards a lot of cards from a player’s hand and i consistently find those very hard to play around if i am unable to meet whatever tests are on them. Mimic is a bit too dependent on a card from another set to really matter, but it is a card from a set that is always used when Secret War is. Finally, Memory Variant only pulls its weight in one of the scenarios unless your deck is particularly vulnerable to having key cards removed (…which is a bad idea in Scarlet Keys in the first place…).
So in total this is a bit of a mixed bag of conditionally relevant cards propped up by a potent mass discard treachery. Fair enough.
I feel like this set is let down by a lack of good payoffs for the hollow mechanic. By itself it’s really good at setting those up however. If there was some other way for hollow cards to matter in one of the encounter sets commonly used with Secret War, the distinction between removing something and having it in the discard would be a lot more relevant.

What it does: Otherworldly Mimic doesn’t engage the player directly, instead it hangs back with Aloof and follows them around with Hunter. While ready and in the same location as an investigator, it will attack that player whenever they play, commit or activate a card which has a copy in the set-aside hollows. This attack deals 2 horror, so it’s rather threatening. Once engaged, it is not all that difficult to defeat.

My take: Otherworldly Mimic tries to go for a similar line of play as the Paradigm Effacer from Agents of the Outside: Hang around aloof, trigger the occasional attack and threaten to come down if the player happens to draw Matter Inversion. I don’t think it succeeds at being as much of a balanced threat as Effacer is, though. For one, it’s ability barely ever triggers, so it’s much easier to ignore and just have it stick around. And if you do want to get rid of it, that’s also much easier, as the difference between 2 and 3 health here is huge. Even if you have to engage it first, defeating it in two actions is not all that difficult. And if you have something like Blood-Rites or Sneak Attack that deals damage to unengaged enemies you can even do it in one.
Mimic has a rather high evasion difficulty, but that matters very little as you’ll very rarely have situations where you evade enemies with Aloof.

Threat level: Low. Mostly a vehicle for Matter Inversion from a different set and often completely ignorable on its own.

Dealing with it: As it has only 2 health and not a particularly noteworthy fight value or combat ability, Mimic is easy enough to handle by a fighter. Most cards that deal damage to enemies at your location are also able to defeat this cleanly and without much fuss.

What it does: Following a failed willpower test, the player has to hollow one card from their hand for each point they failed by. As a silver lining, succeeding by 2 or more allows the player to regain one of their hollows to their hand if they are willing to take 1 horror for it.

My take: This is one of the cards from The Scarlet Keys that i dread the most. As someone who enjoys their low willpower rogues, this card has the potential to just shred my hand. Thankfully it is limited to 3 cards, so it isn’t quite a repeat of Innsmouth’s “Memory of Oblivion”. But it’s still plenty rough. Even high willpower investigators can easily lose a card or two to this treachery and just the threat of an autofail can of course mean the same for anyone.
Secrets Lost gets additional power from being one of the few ways the game has to set up the various hollow synergies on some encounter cards in a consistent way.
Succeeding by 2 or more can get you a card back, which is nice to see on a treachery. It will only rarely come up (it hasn’t for me yet after playing more than 4 full campaigns…) but when it happens it’s going to feel good… that point of sanity you have to pay for the card is a real cost as well, though.

Threat level: Mid. Shreds your hand and sets up various synergies with hollow for further punishment down the road.

Dealing with it: The Scarlet Keys doesn’t test willpower overly much, but when it does the repercussions of failing are fairly harsh. Therefore is pays to have plans for passing a couple of these tests in your decks, for example by including cards like Savant or Defensive Stance in your decks that can give you 3+ icons.
Of course, even a Promise of Power for +4 won’t reliably make a 1 willpower investigator pass this treachery so anyone vulnerable to the treachery should probably anticipate it and keep a couple sacrificial cards in their hand if possible.

What it does: Memory Variant stays in play next to the agenda until an investigator spends and action and succeeds at a rather difficult willpower test. While active, any events played by any investigator is hollowed instead of discarded.

My take: Often you can almost ignore this thing because just losing a couple cards in itself matters only if you use recursion or plan on cycling through your deck often. And even then, it needs to be drawn rather early to have an impact. Getting it in the later half of the scenario is almost a free draw. I say “Almost”, because notably this is one of the better cards for setting up hollow synergies. Also there are a few event based investigators like Sefina or Nathan that will have this become rather worrisome. In terms of payoffs, there isn’t really a whole lot. This set has the Mimic and for Dancing Mad that’s already it. Congress of the Keys adds Substance Dissimilation from the Outsider set as a potent payoff. But the real important scenario for this card is of course Without a Trace where the number of hollowed cards plays into the scenario mechanisms.

Threat level: Low to Mid. Can be a freebie and unless you are playing Without a Trace, this usually isn’t going to impact you too much, …

Dealing with it: … however *when* it does bother you because you are one of the investigators or deck types this targets and you drew it early enough to matter, it’s remarkably difficult to remove. Increasing the difficulty on the test to 4 from the more standard 3 makes this a big bother to get rid off.