Leira, Lady of the Mists

As long as your devotion to blue, white, and
black is less than 7, Leira isn't a creature.
{u}{w/b}{t}: Choose a non-legendary creature. As creatures enter the battlefield, they become a
copy of chosen creature until end of turn.
Exile 20 cards from top of library: Put Leira
from the graveyard to the battlefield.