David, the Chaotic Leviathan

Indestructible, Trample, Menace
Whenever David, the Chaotic Leviathan deals
combat damage to a player, that player exiles cards
from the top of their library equal to the number of
colorless creatures you control, then you may cast
any number of nonland cards exiled this way
without paying their mana costs.
"In the chaos of the void, even the most unlikely
heroes emerge."