Feel free to rub my face in it when this turns out to be wrong, but I see this guy being another Sarkhan Vol. His ultimate is pretty much game over, but he can't protect himself while he builds up to it. His second ability seems like it might be good, but it leaves him on 1 if you use it straight away and if you don't you have to waste a turn with his first ability which is probably irrelevant in a ramp deck and leaves him open to being killed. Plus you need to play a lot of basic mountains to get the best out of him.
I was first excited by this guy, as a way for monored aggro to improve its matchup against UW control mostly, but everyone seems to want it in midrange, which disturbs me as it can't protect itself. in Monored ramp everflowing chalice is the only other ramp card and frankly you want both in your opening hand for a decent draw, RG ramp Garruk would make more sense with the same ramp capabilities for the same cost but garruk can defend itself, and in valakut ramp it doesn't really do anything.