After the war, Revan along with his apprentice, Malak, and the Jedi that followed him, fell to the Dark Side for some reason and sought clues to the mysterious Star Forge. However, the Jedi lured him into a trap...where he was betrayed by Malak and rescued by Bastila.
In some stories in Legend of the Multi-Universe, Revan is a man. In others, Revan is a woman.
Chronicles of the Children of Megatron
In this story, Revan is female and is still a Sith. She is also the wife of Sauron and one of the adoptive great-grandmothers of Darth Menslady.