Streifroef

Trample, hexproof from white
Whenever a player loses unspent mana, put that
many -1/-1 counters on Streifroef.
When Streifroef dies, add any combination of {r} and/or {g} equal to the number of -1/-1
counters on Streifroef. This mana doesn't empty
from your mana pool as steps and phases end.
The fire eats the trees to feed the forest.