There's a slight typo that needs fixing "cratures".
This might be a bit too much elemental love / hate. Comparing this to nightfall, you're only buffing 1 elements, not 2, and you're dealing damage to all the rest. Then again, comparing this to flooding which kills all non-water creatures (except 5) but doesn't buff water. So I'd say this is okay in that respect.
The effect is maybe a it vanilla though. I don't know what you could do to spice it up, if you wanted to. Maybe it's just me.
I also think I've seen the lava idea done before (maybe by odin...) but I can't remember what that one was like.
Overall, a very solid idea