Arcanivore Horde

When Arcanivore Horde enters the battlefield,
return 2 Arcanivores from the graveyard to the
battlefield tapped.
{c}{c}{b/g}: Reviviform valid target Host:
- When host creature attacks, both you and Host
Controller may return a creature from the
graveyard with mana value X or less to the
battlefield tapped, where X equals twice the
number of Revivifaction counters on host
creature.