I'm... torn... about the card. I'll start with the good.
I fully support life finally getting a mono way of swarming. For being an element about swarming creatures, it really lacks an effective method of doing so. And I do love the concept of a tree card, especially Yggdrasil, as I hugely support elven and norse mythos. And I love the ability to duo rustlers, creature spam, and luciferin.
But.
I would never use it. And here's why:
The vast majority of all life creatures cost less than four life. I mean, sure, magically spawning them out the butt for four seems cheap (COUGH COUGH FRACTAL COUGH), but then they /die/. And to top it off, it's not necessarily a life creature. Which means, whereas there is a dragon and a nymph for each element, most elements have other three creatures, tops. In the same way fate egg gets dragons and nymphs more times than not, this will only get OP'd creatures when you play against it, and it will only get PoS when you use. And while I noticed the rebalance percentages you made, I still feel as though more RNG wins are exactly what this game doesn't need.
Also: why isn't it a permanent?