Erm, The Travelling Grove

0: Discard a nonland card. For each of its colors, add one mana of that color to your mana pool and put a loyalty counter on Erm.
-2: Until your next turn, if another planeswalker or creature you control would die, it loses all abilities and becomes a Forest land instead.
-7: Lands you control become 4/4 Elemental creatures with haste, trample and vigilance until end of turn. They're still lands.