Shaman of the Rot

Deathtouch
Whenever a creature you own is put into the
graveyard from anywhere, put a +1/+1
counter on this creature.
{b}{g}, {t}, Remove all +1/+1 counters from
Shaman of the Rot: Create an X/X black and
green Zombie Wurm creature token, were X is
the number of +1/+1 counter removed this
way.