Aritalor, Cosmos of Hues

Devoid
When Aritalor enters the battlefield, you may
turn any number of target nonland cards face
down. As long as they are face down this way,
they're 2/2 colorless Art creatures with "Sacrifice another Art: Turn this card face up."
Aritalor's power and toughness are each
equal to X plus the number of Arts target player controls.