Cliffside Elemental

Whenever a Forest you control is tapped for Mana, Cliffside Elemental gains Trample until end of turn.
Whenever a Mountain you control is tapped for Mana, Cliffside Elemental gains Indestructible until end of turn.
{r/g}{r/g}{r/g}: Put a +1/+1 counter on Cliffside Elemental. Use this ability only once per turn.

As the stones gathered on its skin and the trees grew on its back, so did its strength.