A card poised to take Arkham Horror by storm (get it?).
I don't have to say much. Most investigators will benefit from this, especially if they have any way of off-shoring sanity to other assets (it has been confirmed the "you" is your investigator card).
So if you are a Mystic, Survivor, or Seeker you have assets that can help shield your Key.
Guardians without access to these card pools will struggle, but even they have beat-cops to take a few hits to keep the key around longer.
Rogues also struggle a bit to use this card without those dips due to ally selection, but they have a few things that can work.
Solo, this card is a monster. Multiplayer, you probably will have 1 person who is considering it and is trying to build around it.
Let them. Because once it gets 2 or 3 horror on it, they become hyper efficient.