The Doomvault

Whenever a Demon, Horror, Troll, Ooze,
Leviathan, or Construct enters the
battlefield under your control, put a quest
counter of The Doomvault. Then if it
has 8 or more quest counters on it, sacrifice
it. If you do, you win the game.
An unforgiving challenge, with a treasure more
than worth the journey.