Note: the following was written on assumptions due to my poor attention to detail. I assumed the increase in power was whenever a player played a spell card (seems kind of implied given the name Spell Eater)
I feel procing only on spells is the better version of this
The 0 health may be a bit much, what's wrong with 1? Otherwise give more base damage. Good synergy with Poison. Is the health given before or after? (Dry Spell)
Unsure about consuming quanta per turn. Combined with the 0 health this seems too UP
I was considering that instead of consuming quanta, you'd give it a charge after each spellcast which could be used to gain +1/+1 for 1
. Capable of depleting multiple charges per turn (like Rustler), but then I realized that's worse in a deck that effectively uses these by casting multiple spells per turn
But if you think the 0 health and consuming quanta is needed to combat the potential power of these, then using my charge idea works (the more you use them, the harder they are to maintain)