The Andalite Chronicles (1997) by Katherine A. Applegate was, I think, an offshoot of the Animorph franchise that I read as a kid.
His name is Elfangor-Sirinial-Shamtul.
An Andalite war-prince. The one who gave five young humans the ability to morph into any animal they touch. They are still out there, fighting an evil so powerful there isn't a moment that goes by when they can actually feel safe. Their story continues.
But this is how it all began.
The story that came before Animorphs . . .
The only thing I could remember was the blue centaurs that talked through their minds and ate through their hooves. I don't know if it ticks the rest of your boxes but I think this is the right book.
