ooo, like it, nice idea! Words like Soul are associated with darkness/light but the concept I feel is probably aether. Perhaps change to name to be more eathery? Can't think of anything myself...
I think he meant "aethery"...
Yeah, as 0 hp. It still couldn't devour a BL though. It would have the ability, but it would effectively be useless. The reason you'd do it that way is so Zanz doesn't have to code it losing an ability and then magically regaining it based on the state its in.