Darth Fastus was a Sith Lord of the resurgent Sith Empire.

When Fastus heard about the experiences of the Republic to determine the strengths and weaknesses of various alien species, he sent a subordinate, Major Locke, to investigate on Belsavis. The purpose of Darth Fastus was to resume the research of the Republic on behalf of the Empire, using genetic manipulation, and create the perfect alien fighter.