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.
Arvinox is a mono-black value engine: every end step you exile the bottom card of each opponent's library and can cast any permanent spell you find using mana of any color, effectively turning your opponents' decks into your own. Spend the early game ramping and grinding, then convert that stolen card advantage into board presence and inevitability. As a bonus you can switch it on as a beater by reanimating or stealing opponents' permanents so you control three or more things you don't own.
Relentless, un-targeted card advantage that scales with the number of opponents and ignores color restrictions.
Cheats on mana since stolen permanents can be cast with mana of any color, splashing bombs from every deck at the table.
Effectively immune to creature removal most of the time since it usually isn't a creature.
Slowly mills opponents, providing an alternate decking win and fueling your own reanimation.
Mono-black gives access to the best tutors, ramp, and reanimation in the format.
Seven mana for an engine that does nothing the turn it lands and offers no immediate board impact.
As a non-creature most of the time, it can't block or attack and dodges your own equipment/aura voltron plans.
Enchantment removal and exile (e.g. Farewell, Disenchant) cleanly answer it and it's hard to protect.
Card quality from opponents is random—you may exile lands or off-color spells you can't easily use.
Slow clock; can fall behind fast combo or aggressive decks before the engine pays off.
Legendary Enchantment Creature — Horror
