Lord of the Forest, rare, 13g/19r
Nature, Mage, Swift
Attack: 18
Enemy tower: -4N
Stock: +2N
N = Nature in hand
Summons Wrath of the Forest
-32(!!!) tower, +16 stock and Swift keyword (so its actual cost will be 0), plus ability to be summoned with Nature keyword and summon another rare Nature. Nature is quite strong now, but this card would make Nature decks OP as hell.
Remove Swift keyword, reduce tower damage part to -3N/2 and stock gain to +N. That would be more adequate.