Arcanageist

Dreamcast, Spontaneous 2 (This creature enters the battlefield with two +1/+1 counters on it. At the
beginning of your end step, remove a +1/+1 counter
from this creature if possible. You may tap this
creature while casting an instant or sorcery. If you do,
it pays for {1} of that spell's mana cost.)
Whenever you cast an instant or sorcery spell,
you may put a +1/+1 counter on target creature
you control.