Diablos

Planeswalker Bestow {3}{b}{b} (If you cast this card
for its bestow cost, it's an Aura spell with enchant
planeswalker. It becomes a creature again if it's not
attached to a planeswalker.)

Flying

Diablos's power is equal to your devotion to
black. (Each Black in the mana costs of permanents you
control counts toward your devotion to black.)

Enchanted planeswalker gets "Mug -[-2]: Gain
control of target artifact."