It's So Fluffy You Gonna Die

At the beginning of your upkeep, put a fluffy counter on It's So Fluffy You Gonna Die.
Whenever you buy a Unicorn, put a fluffy counter on It's So Fluffy You Gonna Die.
Remove 5 fluffy counters: Destroy all permanents you don't control.
"It's so fluffy you gonna die!" - Agnes, Despicable Me