I could have sworn I already commented on this? It's ridiculously powerful. Creates 8 power of creature a turn, allows those creatures to buff, and the only cost is giving up something that doesn't normally exist anyway; and not attacking with this itself which you'd obviously never do anyway).

So on the plus side - it's now a 6-cost legendary. And the opponents do get a chance to deal with it before it goes off. (I think? When is your first fossil untap phase?)

So maybe it's reasonable? It's sure as heck splashy.

I pretty much followed your suggestions and just copy-pasted the original text into the mythic slot and put a different rare in its original slot.

Confusing to create a new card rather than edit the existing one.

Only just now did I remember I can edit the skeleton to do that.