Sulfurous Thicket
Land-Swamp Forest (Rare)

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

When Sulfurous Thicket enters the battlefield, sacrifice it unless you pay B.

2: Sulfurous Thicket becomes a 2/2 green Squirrel Treefolk creature until end of turn. It's still a land.

Greg Staples