Denolm Orr was a Human male Jedi Master who was the mentor of Sa'har Kateen. During the third Galactic War, Orr was killed during a mission to retrieve a holocron from the Temple of Nul by the renegade Sith Lord Darth Malgus, who tried to turn his Padawan against him.
Denolm Orr was a member of the Children of the Emperor who carried out various atrocities in the Emperor's name. Denolm was later freed from the influence of the Emperor and joined the Jedi Order to which he only revealed his past to Jedi Master Gnost-Dural who agreed to conceal the information. Denolm Orr later made it his personal mission to eradicate the dark presence of the Children starting from its creator: Darth Nul.
Denolm's padawan Sa'har Kateen
Sometime before the third Galactic War Jedi Master Denolm Orr encountered two Force-sensitive Twi'lek children. He took the girl as his Padawan and left the boy behind as his connection to the Force wasn't strong enough.
After Darth Malgus's theft of relics from Great Jedi Library and Dantooine Jedi Enclave, Task Force Nova discovered that the stolen items came from the planet Elom and belonged to Darth Nul, a mysterious Sith who the Republic didn't have any records of. Denolm Orr assembled a team consisting of Jedi Master Gan Enok, Material Analysis Dr. Mykon Ora, Chief Engineer Rolan Aun, Specialist Tiriz Etto, and his Padawan Sa'har Kateen in search of Darth Nul's creations. During their mission, the team encountered Imperial forces. By the time they reached the Temple of Nul only he and his Padawan were alive. They went to the device they found inside when Darth Malgus appeared and killed the Jedi Master. Before his death, he managed to destroy the machine, but Malgus still managed to get his hands on the holocron that was inside of it.