Nice idea, but imho even with the already suggested modifications it stays OP.
Imo there are 3 really strong creature damaging abilities: momentum, immaterial and growth.
I think NO creature EVER should (and probably will) have any two of these build in by default.
I see two ways to balance this card:
1) Remove immaterial
2) Change it to:
This creature becomes immaterial for 1 turn.
As there already are Creatures with growing HP (like Scarab) you could another route: Fix its HP to a very low amount, 1-3 perhaps, not more.
Furthermore, i agree with the previous posters that it should be MAX. N/5...so this wont become the uber rush card. And increase quanta costs. The previous suggestion 10 normal, 8 upped sounds good.
And i would try some different name...such Names are reserved for enemies, not creatures...maybe something like Strom Giant, Lightning Elemental (both dont fit really well...)...or what ever the theme of this creature should be...though the name should contain something airy^^