Arvinox isn't a creature unless you control three or more permanents you don't own. At the beginning of your end step, exile the bottom card of each opponent's library face down. For as long as those cards remain exiled, you may look at them, you may cast permanent spells from among them, and you may spend mana as though it were mana of any color to cast those spells.

Flying When this creature enters, destroy target nonblack creature. It can't be regenerated.

Other white creatures you control get +1/+1. Other black creatures you control get +1/+1. Whenever you cast a white spell, you may tap target creature. Whenever you cast a black spell, you may destroy target creature if it's tapped.

Whenever a creature dealt damage by this creature this turn dies, return it to the battlefield under your control. That creature is a black Zombie in addition to its other colors and types.

Trample Whenever this creature deals combat damage to a player, you may look at that player's hand. If you do, you may cast a spell from among those cards without paying its mana cost.

Whenever this creature attacks, defending player mills ten cards.

Trample Whenever this creature is dealt damage, sacrifice that many permanents.

Trample Whenever a source deals damage to this creature, that source's controller sacrifices that many permanents of their choice.

Whenever this creature enters or attacks, put a slime counter on up to one other target creature. Non-Horror creatures with slime counters on them lose all abilities and have base power and toughness 2/2.

{U/P}: Change a target of target spell or ability to this creature. ({U/P} can be paid with either {U} or 2 life.)

This spell costs {3} less to cast if it targets a tapped creature. Destroy target creature.

{T}: Add one mana of any color in your commander's color identity.