Treetop Key
Land-Forest Island (Rare)

(Tap: Add G or U to your mana pool.)

Treetop Key enters the battlefield tapped unless you control one or more Merfolk.

2G, Tap: Target green creature gains trample until end of turn.

2, Tap: Target land becomes a 3/3 blue Crab creature until end of turn. It's still a land.

Eric Critchlow