Leo started out on the show as the Charmed Ones' Whitelighter.Then he became and elder Leo died during World War II. Then he was reborn as a whitelighter. He was a medic in the military. After being the Whitelighter for the Charmed Ones for several years, Leo was elevated to the position of Elder. He later joined a group of beings called The Avatars. By the end of the series, he had fallen from grace and was made mortal again. He has killed two Elders and many demons to protect Prue, Piper, Phoebe, Paige, Wyatt and Chris.