From Spyropedia
Red the Fallen Dragon Elder is the main antagonist in Spyro: A Hero's Tail, while also appearing in Spyro: Shadow Legacy, also serving as an antagonist.
History
According to the other elders, Red was once a Dragon Elder like them. It was only when his jealousy and hunger for power led to an attempted over-throw of the elders' leader. As a result, Red was banished from the Dragon Realms and forced into hiding for many years.
After Spyro's adventure in Attack of the Rhynocs, he and the Professor (having a new lab stationed in the Dragon Realms) witness both Red and Gnasty Gnorc return from exile, along with a new army of Gnorcs and a mined stash of Dark Gems at their disposal. By spreading the Dark Gems all over the realms, they suck the life out of anything it touches, which the Professor states will fuel Red's evil power.
It's later revealed that Red's been controlled by the Sorcerer all this time, and will teach Spyro a new move after being defeated. He is later welcomed back by the other elders (exept Titan).
Trivia