Chaskar was a male Pureblood Sith Overseer who served the Emperor of the reconstituted Sith Empire during the Galactic War with the Galactic Republic.
When the Jedi Knight known as the Hero of Tython was captured along with the other members of a Jedi strike team sent to capture the Emperor himself, Chaskar was appointed as one of the Knight's teachers in the ways of the Sith aboard the Emperor's Fortress. After some time, the Hero broke free of the Emperor's mental control with the help of the Force ghost of the Jedi's former Master, Orgus Din. Chaskar called the Knight to another training session, unaware that his student had broken free from the Emperor's influence. During the session, in which the Hero was to torture Kira Carsen for information, the Knight was able to influence Chaskar into departing so that the Hero and the Jedi's allies could escape the station.
Chaskar appears only in the Jedi Knight class mission "An Unthinkable Alliance," which bridges the gap between Acts II and III for the class in the BioWare–LucasArts video game Star Wars: The Old Republic. There were three options to get rid of him. The first two were the light side options of either mind tricking him to leave or knocking him out, while the third dark side option was to kill him.