Festering Crypt

Festering Crypt enters the battlefield tapped.
{t}: Add {b} or {g} to your mana pool.
{4}, {t}, Return Festering Crypt to your hand:
Create a 1/1 Insect creature token with
Hatching 1. (At the beginning of each upkeep,
if a creature died last turn, this creature creates
a copy of itself.)