Lytos was an Ilytian eunuch and a Blackguard. Before his death, he was in a secret relationship with Fisk: a Blackguard trainer and later watch-captain and eventually commander of the Blackguard, after Ironfist's disappearance. Knowledge of this illicit (forbidden,) relationship was used by Andross Guile to blackmail Fisk into acting as one of Andross' pawns.
Lytos was described by Karris White Oak as lanky, with a crooked smile. He was a practical joker with an infectious laugh, with a penchant for pulling pranks and practical jokes on the new Blackguards, such as putting firebalm in their underclothes and putting live scorpions (with their stingers sealed,) in their boots.
After Lytos and Buskin betrayed the Blackguard by attempting to assassinate Kip Guile, (motivations unknown,) Lytos was killed by an arrow to the chest. As both Cruxer and Winsen were armed with bows at the time, it is possible that either of them may have fired the shot that killed him. Kip later states that it was Winsen.
When Karris debriefs Kip regarding the betrayal of Lytos and Buskin, their attempted assassination of him, and their subsequent deaths, Kip states that he thought he heard Lytos say: "fuck it; I can't do this." It is known that Lytos drew his knife right before he was killed; Kip believes it is possible that he was drawing it to attack Buskin in defense of Kip, having come to his senses and regretted his betrayal.
When Fisk reveals to Teia that Andross knew about his and Lytos' relationship, Teia asks if Andross used that to blackmail Lytos into attempting to assassinate Kip. Fisk beleives that he did not, as he had previously confronted Andross about the matter, and Andross stated that not only had he not blackmailed Lytos, he had never talked to him. Andross went on to say that to ruin a eunuch's reputation would be like an emperor stealing a gold ring from a beggar; it would change nothing for the emperor, but the beggar would likely never have another such opportunity. It would show a meanness of spirit that Andross did not wish to partake in to ruin such happiness, even if Andross did not understand it. Fisk believes this is evidence that, while Andross is not a good man by any definition and is ruthless, he is not cruel for cruelty's sake.
As a result, Lytos' and Buskin's motive(s) for their betrayal remain unknown. Fisk does not rule out the possibility that someone else found out about him and Lytos and used that against him, since neither Lytos nor Fisk could have lived with being expelled from the Blackguard in disgrace. No explanation has been offered for Buskin's betrayal.