Farwil Indarys was a Dunmer and the son of the Count of Cheydinhal. He was the leader of the Knights of the Thorn and believed his knights were capable of anything; therefore, when an Oblivion Gate opened up outside Cheydinhal, he and his knights rushed in to close it with heavy losses.
Head through the west gates of Cheydinhal to help Indarys and the Knights of the Thorn close the Oblivion gate. He is found alive with one other knight in the Oblivion gate, and a choice must be made to save him or let him be killed.
If the choice is made to save him and make sure he survives the quest, he will award the Hero the Knights of the Thorn Medallion as well as the choice of taking the leveled Staff of Indarys or the Thornblade.