Toxic 2

Whenever a creature is put into a graveyard exile it and put a plague counter on it.

At the beginning of your upkeep you may put a creature with a plague counter on it from exile onto the battlefield under your control. If you do, it becomes an Artifact and is a vehicle with crew 1 in addition to its other types.

{B/G}{1}: Create a 1/1 green Wurm creature token.