The Annexation of Kiffu was a conflict after 3653 BBY during the Cold War in which the reconstituted Sith Empire forcibly took control of the Kiffar homeworld of Kiffu.
It is implied through dialogue in The Old Republic: Fatal Alliance that Darth Chratis played some role in the annexation of Kiffu. However, this has never been confirmed, and the context of the dialogue itself makes its reliability questionable. Darth Chratis claims to Shigar Konshi that his anger toward Chratis for the subjugation gives him power, and when Konshi replies that this is false, as Chratis played no part in the annexation, the Sith Lord simply replies "Didn't I?" However, Chratis may have been lying in order to further encourage Konshi's anger and so lure him down the path of the dark side of the Force.