He's one of the strongest force-users known to have existed. He first rose to prominence during the Mandalorian wars, known as a brilliant general and charismatic leader, though his actions flew in the face of the Jedi Council of the era, leading to himself and many others who followed him being exiled from the order and stripped of their connection to the Force. However, he and his apprentice both took up the mantle of Sith Lords, and began a campaign against the Republic forces of the Era. However, he was later captured in a raid by a rising star of the Jedi, Bastila Shan, although a good portion of his defeat is due to his former apprentice, Darth Malak, turning on him and firing on his flagship. When Revan was recovered, it was discovered that he had been rendered amnesiac when his ship was lost. Revan was implanted with false memories, and sent onboard the ship known as the Endar Spire... The rest, as they say, is history.

Cool. Thanks for explaining that!