Creatures with power 7 or greater can’t attack or block.
Whenever chaos ensues, create a 7/7 colorless Eldrazi creature token with annihilator 1. (Whenever it attacks, defending player sacrifices a permanent of their choice.)
A creature's power is checked when attackers or blockers are declared. Increasing the power of an attacking or blocking creature to 7 or greater won't remove that creature from combat.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.