Elfangor-Sirinial-Shamtul is a character in K. A. Applegate's book series Animorphs. He is of an alien race known as the Andalites. His adventures are highlighted in the book The Andalite Chronicles, which takes place before the main Animorphs series.
Elfangor is an Andalite war-prince, the one who gave five young humans (who would become the Animorphs) the ability to morph into any animal they touch in order to save Earth from the parasitic beings known as the Yeerks. Elfangor's son is a human boy named Tobias—one of the Animorphs. During a time when Elfangor was stranded on Earth, he morphed into and became a human (with the alias of "Al Fangor"), and it is implied that he finds work in the computer industry with a man named Bill and is responsible for most of humanity's recent advances in computer technology. He marries a woman named Loren, who was a teenager when she was saved by Elfangor after being kidnapped from Earth by a crew of insect-like Skrit Na. Tobias is their child. Elfangor also has a little brother named Aximili-Esgarrouth-Isthill, who later joins the Animorphs and is just called "Ax" for short.
In his great adventures, Elfangor meets many strange, wondrous, and mysterious things. He comes into contact with the Ellimist, a god-like being capable of altering the strands of Time itself. He also gets an archnemesis, a Yeerk by the name of Esplin 9466 Primary. (When Elfangor first met Esplin, Esplin had the rank of Sub-Visser Seven and inhabited the body of a Hork-Bajir. Esplin took over the body of the Andalite war-prince Alloran-Semitur-Corrass and advanced to the rank of Visser Thirty-Two. He soon became Visser Three, and near the end of the Animorphs series, he attained one of the highest ranks of the Yeerk Empire—that of Visser One.)
Elfangor was promoted from the rank of aristh (the Andalite word for cadet) to the rank of warrior for ramming the Blade ship of Visser Three with a small fighter ship and disabling it, thus saving an Andalite dome ship. Elfangor eventually attained the rank of war-prince, the highest Andalite military rank.
Elfangor's demise comes in his final battle with his nemesis, Visser Three (Esplin). Elfangor's fighter ship is damaged and crash-lands onto Earth, greatly injuring Elfangor. Elfangor, knowing that the Yeerks will soon try to conquer Earth and enslave the humans, gives five young humans who just happened to be in that empty construction site the ability to morph, or turn into any animal they touch. These five humans were Jake, Rachel, Tobias (Elfangor's unknowing son), Cassie, and Marco. Soon thereafter, Visser Three arrives and uses Alloran's body to morph into a monstrous creature called an Antarean Bogg (genetically created by the Arn, the same species that also created the Hork-Bajir) and devour Elfangor.