Ironroot Greenskeeper

Ironroot Greenskeeper counts as an artifact, can
be played once a turn if you've already played a
land this turn, and enters the battlefield tapped.
Indestructible, Trample, Shroud
Whenever you cast a green creature spell, you
may add {g}, put a +1/+1 counter on Ironroot Greenskeeper, and gain 1 life.
"Storms make trees take deeper root."