Copperline Marsh
Land (Rare)

Copperline Marsh enters the battlefield tapped.

1, Tap: Add GG, GB or BB to your mana pool. Copperline Marsh deals 1 damage to you.

2G: Copperline Marsh becomes a 2/2 black and green Bear creature with trample until end of turn. It's still a land.

Ron Critchlow