Nocturnal, Prince of Night

Indestructible
Nocturnal, Prince of Night can't attack or block
unless your devotion to blue and black is seven
or greater.
Whenever a creature deals combat damage to an
opponent, target player discards a card and puts
the top four cards of their library into their
graveyard.
"Night among strangers. Secrets in the dark.
Nocturnal is here."