Hooray, always felt like Dark/Earth was missing something. Now it has it all. Stalling, a good hitter (The big problem), Quanta drain, burrow, and extreme permanent denial. It looks like it's more designed to be an Earth compliment, although it still works either way.
As is, I feel that if it's only one use, like lycanthropy, then it's probably pretty balanced, although it could start off with 1 hp, or 2, so it survives Fire Shield. If it's re-usable, then it's only good with a stasis effect. The optimal number there would be 4 turns, since with adrenaline it gets 3, making it un-abusable that way, since from that point flying druids become better targets for adren, and you still get the +20 per turn.