Demonomicon

Other commander permanents you control have "Whenever you Venture Into The Dungeon, you
may pay 2 life. If you do, until end of turn
replace its room text with 'Create a 1/1 Black
Demon creature token with Reach and Riot'."
Sacrifice X creatures: You become the Monarch, unless the Monarch sacrifices X creatures.
(Activate only as a Sorcery)