Chaskar was a male Overseer of the Pureblood Sith species. He served the Emperor during the Galactic War between the reconstituted Sith Empire and the Galactic Republic. He is considered a male in legend.
Chaskar was assigned as an instructor to the Jedi Knight known as the Hero of Tython after the Knight's capture. The Knight, along with other members of a Jedi strike team, had been captured while attempting to capture the Emperor himself. Chaskar's assignment took place aboard the Emperor's Fortress. After a period, the Hero managed to break free from the Emperor's mental control with assistance from the Force ghost of their former Master, Orgus Din. Unaware of this development, Chaskar summoned the Knight to another training session. During this session, where the Hero was meant to torture Kira Carsen for information, the Knight used the Force to influence Chaskar into leaving, enabling the Hero and their Jedi allies to escape the station.
Chaskar's sole appearance is in the Jedi Knight class mission titled "An Unthinkable Alliance." This mission serves as a bridge between Acts II and III of the Jedi Knight storyline in the BioWare–LucasArts video game Star Wars: The Old Republic. Players had three options for dealing with him: two light side options (either using a mind trick to make him leave or knocking him unconscious) and one dark side option (killing him).