Leech's Host

Whenever you cast a black creature spell, put
a -1/-1 counter on up to one target creature
you don't control. Then put a +1/+1 counter
on up to one target creature you control.
Just going near this bog can be deadly, whether
you step in a puddle or go for a dip, the leeches
are quite deadly in numbers. ~Rokalos Vidakro