Morto had joined Darth Krayt's One Sith by 27 ABY, as he had trained under Lomi Plo, who disappeared in that year. In 40 ABY, his feelings for his former Master were still strong, so much that he had been in love with Lomi Plo.
By this date, Morto was serving as the gatekeeper of the Sith complex in the Valley of the Dark Lords on Korriban. Although he had been a Sith for over a decade, Alema Rar's arrival at the fastness was treated as a practice session for him, making it possible that he was still regarded as a learner.
The Togorian initially bested the Twi'lek Jedi Knight, but he was called off by a high-ranking female Sith, in order to allow White Eyes to interrogate Alema. Once the questioning was concluded, Morto was ordered to fight and kill her, but Alema managed to persuade the Sith to let her live—and when the Togorian was about to stand down, he was flung violently against the walls of the courtyard by White Eyes, believing that he failed to obey.
After the initial attack, Alema had given him a vial, the contents of which he spread onto the dart wound she had inflicted, assuming it to be an antidote for the toxin. Instead, she had actually provided him with flesh-eating bacteria from Tenupe in exchange for his earlier revulsion to her deformed appearance.
Tall, muscular, and physically impressive, Morto wore a dark cloak and armor. His fur had been shaved to display a pattern of Sith tattoos.
Morto was armed with a lightsaber, and was strong enough in the Force to pin down a trained Jedi Knight with Force Crush and to resist the painful effects of a poison dart.
- The Complete Star Wars Encyclopedia