Here's what I've written of Don't Rest In Shadows thus far:

Introduction (6 short paragraphs)

Secrets:
Secret of Hypnochondria, Secret of Red Things Obey Me, Secret of Shadow Jumping, Secret of Bat Wings, Secret of Animal Speak, Secret of the Mentor, Secret of the Master Plan, Secret of Primacy.

Antagonistic Keys:
Key of Vampiric Assassins, Key of Troll-Thing, Key of the Savant Guard, Key of Ribbon Fox, Key of The Torches.

Bold stuff, I wrote today.
Yay!

Don't Rest In Shadows, my DRYH+TSoY mashup that tells young adult fantasy stories (with a huge emphasis on power, danger, corruption and the responsibilities of heroes) has this thing called Antagonistic Keys.

When confronted by an enemy, or after taking down an enemy, or after hearing mention of such an enemy, you can buy one of these Keys. I just wrote the first example. They will all follow (tightly) this formula.

Key of Vampiric Assassins
You are being pursued by a cadre of vampiric assassins. They may work in tandem, or as isolated threats.
Gain 1XP whenever you introduce information about the assassins' involvement in the plot at hand.
Gain 3XP whenever you frame the vampiric assassins into a scene.
Gain 5XP whenever you attempt to befriend or support the assassins, and it proves to be a bad idea.
Buyoff: Shake the vampiric assassins for good.

Thoughts? I'm noticing that the 3XP and the 5XP bars would likely chain together a lot of the time, which might provide balance issuse.
Maybe I want to change the 3XP bar to "whenever you introduce an attack by the vampiric assassins into a scene"?

Regardless, I really like this idea. The rule is that the GM cannot introduce a monster/enemy/threat into the game more than once, unless someone has it as a key. And they can't take it as a key unless the GM has introduced it into the narrative. So, there's a feedback loop, where the GM throws a bunch of cool enemies out there, the players latch onto some, and are then rewarded with XP for complicating their own stories with these enemies.