Yeah, it's conditionally powerful, because it's pretty easy to clog your hand with hourglasses, discard them to play them, and then clog your hand using hourglasses. Plus, one card per turn is enough, as all you need is one sky blitz to discard. Just wondering, if you discard something like sky blitz or fractal, do you lose all quanta in that element? If you discard a targeting spell, will targeting occur before your creatures attack?
And I never said it was overpowered, as I added the clause "if not destroyed", which means that I'm disregarding the cost of resilience towards destruction and only evaluating its effect. While it may very well be balanced, I still think that you should have to pay a cost for each card you play this way.
Edit: Thanks, added it to the series.