Aethervoid

Aethervoid enters the battlefield with two depletion counters on it.
{t}, Put two depletion counters on Aethervoid:
Add {c} to your mana pool.
{t}, Remove a depletion counter from Aethervoid: Add one mana of any color to your mana pool.
{t}, Remove seven depletion counters from Aethervoid: Your mana pool doesn't empty as steps and phases end.