Mask, god of thieves

Indestructible
As long as your devotion to blue and to black is less than seven, Mask, god of thieves is not a creature.
Whenever you cast a rouge, target opponent reveals their hand and you select a card from among them. Put the selected card under this card in exile. When this card leaves the battlefield, return the selected cards to their owners graveyard.
{1}{u/b}, sacrifice a creature: create a treasure token with “{t}, sacrifice this artifact: add one mana of any color.”.