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 At the beginning of your end step, exile the top card of each opponent's library. You may play those cards for as long as they remain exiled. If you cast a spell this way, you may spend mana as though it were mana of any color to cast it. Whenever a nonland permanent an opponent owns enters the battlefield under your control, they lose life equal to its mana value.

Flying When this creature enters, exile target card from an opponent's graveyard. If it was a creature card, that player loses 1 life.

{0}: If this creature is tapped, exile target creature card from a graveyard and untap this creature.

Menace Whenever this creature attacks a player, exile all cards from that player's hand, then they draw that many cards. You may play lands and cast spells from among the exiled cards for as long as they remain exiled. If you cast a spell this way, you may spend mana as though it were mana of any color to cast it.

When this creature enters, exile another target creature. When this creature leaves the battlefield, return the exiled card to the battlefield under its owner's control.

When this creature enters, exile up to two target cards from a single graveyard. When this creature leaves the battlefield, return the exiled cards to their owner's graveyard.

Whenever this creature attacks, exile target card from defending player's graveyard.

Flying When this creature enters, if you cast it from your hand, exile all cards from target opponent's hand. When this creature leaves the battlefield, return the exiled cards to their owner's hand.

Devour Intellect — When this creature enters, each opponent exiles a card from their hand until this creature leaves the battlefield. Body Thief — You may play lands and cast spells from among cards exiled with this creature. If you cast a spell this way, you may spend mana as though it were mana of any color to cast it.