Have you guys noticed that Rockwing and his mate, Birchcloud, never have colts only fillies? And after Petalcloud abandons Frostfire to Rockwing she becomes barren? I think the Ancestors of Anok have power over living pegasi. I think they watched over the steeds and saw Rock wing get nasty and they knew he would make his colts the same monsters he was. And they cursed Petalcloud then she betrayed her colt. But the Ancestors had pity on Frostfire because he was forced into bullying. His true nature was revealed when Starfrost became known. His love was revealed
In the third book (spoiler alert), Nightwing and Petalcloud's dead colt is black. How is that possible, even if he was stillborn?