Before the Animorphs there was Elfangor.

Elfangor-Sirinial-Shamtul is an Andalite war prince--the one who gave the Animorphs the power to morph. "The Andalite Chronicles" is the story of how this warrior-cadet ended up on planet Earth Ages 9-12. Pub: 12/97.

We found out who Visser Four is. And he has found the Time Matrix, the machine Elfangor had hidden in the abandoned construction site. The same place we met him on a night none of us will ever forget. Especially me. Now Visser Four has the Matrix, and he plans to use it to become Visser One.But Jake, Rachel, Cassie, Marco, Ax and I can't let that happen. We can't let him alter time so that the Yeerks will win the invasion. So we're prepared to make the ultimate sacrifice. Eventually, one of us will lose this fight...

The tale of Elfangor-Sirinial-Shamtul, an Andalite war-prince and the story of his beginnings.

Elfangor travels to the Taxxon home world and encounters Sub-Visser Seven.