Nothing besides the mentioned duality. It's fine as it is. I meant that this is not a creature for fractal, but has some good synergy with blessing, chaos power, momentum and adrenaline.
Maybe we should summon Oldtrees here ^^ but I think that the cost could still be lowered:
I would say that invisible, as it is better than inmortal, has to get a +3 cost. But you need an specific card, so it reduces the cost by 2 (3 if you consider the Nightfall suggestion, because it is from a different colour). Then you have the -1 life bonus.
So the cost (with my maybe wrong maths) is 1 for the unupped and you could rise to 2 the attack of the upped.
mmm is it right?
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Oldtrees!! Help! XD