Anaashrak, Mariners Folly

At the beginning of each upkeep, put a Prey
counter on target permanent.
Whenever a permanent with a Prey counter is
put into a graveyard, that player reveals cards
from the top of their library until they reveal a
card of the same type, then puts those cards into
their graveyard.
It took years to muster the army, but moments for it
to be destroyed.