Andreaus Thos was a Sith Lord of the Sith Empire, a Pureblood male who existed in the era of the Galactic War. Circa 3641 BBY, he received orders to lead the Special Operations Group One into Belsavis prison with the objective of liberating the imprisoned Dread Masters. After a successful breach of the Tomb, Lord Thos took a portion of his team to free Sith inmates held within stasis block 44. Republic troops, working alongside the privateer Zale Barrows, launched an ambush on Thos's squad, almost annihilating them. However, the opportune arrival of a bounty hunter who was tracking Barrows shifted the battle against the Republic forces, enabling Thos to proceed with his assignment.
Lord Thos is featured in Star Wars: The Old Republic as part of the Bounty Hunter storyline on the planet Belsavis. Scrapped content found within the game's data suggests that he was originally intended to appear in the Bounty Hunter story on Sleheyron, but this content was ultimately removed.