So... this thing does some pretty funny things.
It's hard to go into much detail without some spoilers, but among other things your whole party can probably ignore a particularly annoying encounter mechanic in Dunwich as long as the fastest-cycling deck has ONE copy of this card. And when searching for dream cities in the dreamlands there's another trap you can just waltz through. When this card works, it tends to be the key to your Locked Door.
It's very likely you're going to blank the discard condition for the card, so it is a stall unless you can push the game state to the point where something is either less relevant or irrelevant. That happens a lot though. And its cheap as dirt if you don't need the slot.