Elfangor

Elfangor is an Andalite alien. He has the body of a deer with a human torso, resembling a gaunt centaur. His fur is blue. Instead of a horse's tail, he has a scorpion's tail with a sharp blade that he uses offensively. He has no nose or mouth, and possesses two pairs of eyes: two on his face and two on his antennae.

He has migrated from his home planet to Earth to raise an army to fight the Yeerks, alien slugs that invaded his home. These slugs can control living beings, manipulating their actions and torturing their original bodies.

To confront them, Elfangor grants his chosen ones the ability of "metamorphosis": every time they touch an animal they absorb its DNA, so they can transform into it simply by remembering it.