This is already in the crucible, but I'm going to comment on it anyway.
Firstly, I LOVE IT!
Minor Phoenix Egg's are much better than a Minor Phoenix in a Lava Destroyer rush because you now only need 1 tower 1 egg and 1 cremation to get it started, adding to the percentage of time you can rush them turn 1. When your BLight's are hiding, these might not be. On top of that, you start of with additional damage and not a 0/7 ash. Destroyer Rushes are already the fastest rushes around, as proven by V2 - Fire Tweaked to Max Speed. This card can improve start up efficiency and increase damage potential, making it the dream card of all Pyromaniacal Rushers.
That being said, this card is definitely OP. Enough people already have issues with Cremation + Minor Phoenix, claiming that it's too cheap. The idea behind Cremation was for you to lose some to gain some. The skill Revive completely cheats on that account. And this card hatching into a creature that has Revive, while giving you quanta, is just... too much. As much as I would love to use this, I must admit that it seems too powerful to be balanced. Looking at its unnupgraded form, you can make use of nearly half cost Phoenixes in like, a Phoenixbow. This in itself is insanely OP.
*edit*
Actually, my first thought was a 0 cost hatch ability, but that makes Phoenix Egg way more OP. My intention was to get out cheaper Phoenixes after waiting 1 turn to do the hatching, but that means that Fractal is way too powerful. INSANELY powerful. While yes, the enemy has a shot at killing the combo, if they don't get it done pronto, they're @#$%ed.
Now I'm at a loss as to how you can balance this. It makes no sense to have an egg that effectively gets you a Phoenix for the same cost, so it would need to be cheaper. Yet at less cost, generating Phoenixes is OP with Fractal. And at the same time, it seems like waiting x turns for it to auto hatch is just as bad, because most people that use fire are looking for speed. The way you have it now, requiring a fire spell to activate it seems like the best idea, yet still insanely OP when used correctly. The only other option is for it to die permanently when hit with Immolation/Cremation but live on as a Phoenix/Minor Phoenix if hit by the others.
Note: This entire speal was for the benefit of the Trials. The card is still epically awesome in my mind.