The Dark Power, which is the source of the purple color in Spyro, is not transmitted by blood ; every 10 generations, a dragon is infected with the power and turned purple while in the egg.
So your OC should be black or some other color, not purple. Likewise, he should be unable to use more than one element. He may use variations of one element if he is heavily modified (as Cynder was) but otherwise, I am afraid that your OC cannot work in the setting.
And I wonder why you used a base. Is it because you're not capable of creating your own dragon from scratch?
I never heard of these 'rules' and where on earth did you get the whole 'turned into purple while in egg' and cynder going through rituals to have all those powers? Anybody can make creative characters, there are no rules, and wyverns don't exist in the spyro world, unless your talking about the enemies, where I fail to see dragons breeding with them. And their are other dragons(the gaurdians and those other ones who appeared in dotd).
But other than that, there are no set rules, and as far as the base goes, some people have issues drawing and prefer bases. Nothing is wrong with that.
I can, but I was bored and used a base. I will draw this soon. I do know about the 10 generations thing, but I just wanted to visually show she was/ is related to spyro. Also, Cynder and spyro are both powerful so maybe this dragon would be powerful to. Finally, there are no set rules, anyone can make up anything so it doesn't matter. And it's nice to put your own tweek on it anyway.
The big problem is that 'their offspring is purple' is not original. It's extremely, painfully overused.
If you want to showcase that he's related to them, it's actually... not difficult at all ; the dragons were basically exterminated, leaving only Spyro and Cynder as pure-blooded dragons capable of producing offsprings (all the other dragons outside of the Guardians are half-wyverns who were spared by the apes' rampage).
And a dragon does not need to be purple to be insanely powerful ; Cynder is not purple (black dragoness) and yet has crazy powers. It is true that she was infused with dark power artificially in extremely painful rituals from a young age but she's the proof that one does not need to be a purple dragon to be incredibly powerful (in fact, she even get access to the Darkness Stream breath attack (giant purple laser) in Dawn of the Dragon, an attack supposed to be exclusive to purple dragons).
I'm not saying you shouldn't make this character. I'm just trying to warn you about the problems caused by making your character purple in terms of the setting.