Yacati, Primal Retribution

Enrage - Put a prey counter on target creature an opponent controls.
{1}{b}, Sacrifice a creature: Target creature get
-X/-X until end of turn, where X is the sacrificed creature's power.
When a creature with a prey counter dies, add {g} to your mana pool. Until end of turn, this
mana doesn't empty from your mana pool as
steps and phases end.