Gam-gam, Elemental Shaper

On your turn, Gam-gam, Elemental Shaper becomes a Fire Elemental with Trample and a power and toughness equal to the amount of green mana used to cast Gam-gam and the text, "When this creature deals combat damage to a player, put a +1/+1 counter on Gam-gam, Elemental Shaper.