@tootjard the Fae, if you do some work to replace promises with riddles. The Ghoul, with a hunger for answers. Or the Wyrm, who can bargain for information.
I suspect a Sphinx will require hard compromises for #monsterhearts - what would the less-competent "teenager" version of something that powerful and inhuman look like?
Keywords that would need to be met - merciless, treacherous, guardian, riddles.
I could see moves involving both betrayal and protection.
A true form that was a rampage would be too similar to the werewolf.
@sev
Replaces promises with riddles looks like a good start.