The Animorphs were a group of five teenage human children, chosen by Elfangor-Sirinial-Shamtul to fight against the Yeerks' invasion of Earth. Later joined by Elfangor's brother Aximili-Esgarrouth-Isthill, the group used the Andalite morphing power given to them by Elfangor to wage a guerilla war against the Yeerks and their leader on Earth, Visser Three. Their actions ultimately ended the Andalite-Yeerk War.