The Miasma Titan

Creatures you opponents control enter the battlefield with a -1/-1 counter on it.
{3}{w}{b}{g}: For each creature with a -1/-1 counter on it, you gain 1 life and each opponent loses 1 life.
When The Miasma Titan dies, you may exile it.
If you do, return it to the battlefield at the beginning of the next upkeep.