A group of Jedi, as described here, battled a group of Dark Jedi (see this page) and Sith (further info here) on the world of Kesh (more on planets here). This occurred following a crash landing sometime after 6900 BBY. These opposing sides clashed on Kesh, and these battles caused immense damage to the indigenous Keshiri species (more on species here). This destructive period became known as the Great Calamity. Every fighter except one, the Sith Lord Remulus Dreypa, consented to cease fighting to protect the Keshiri. Because Dreypa refused, he was imprisoned in an oubliette. The surviving Force users combined their numbers, becoming the Doomed, and dedicated themselves to safeguarding the Keshiri people.