Morith, the Infected Infector

Player, Wither (This creature deals damage to creatures in the form of -1/-1 counters.)
{1}{b}{g}, {t}: Put a -1/-1 counter on target creature.
Mana Pool - {b} or {g} (During your untap step add {b} or {g} to your mana pool, this mana doesn't empty
as steps, phases, and turns end.)