
Indeed, during the mission “Fortification” as part of the Imperial Storyline for Legacy of the Sith, you can run into a captured Arn Peralun and Colonel Gallo.
Just after you first meet Korrd, as you travel back to the regular underwater zone after you have completed the submarine probe segment, you can find Lord Tarnux standing infront of the duo near a supply rack of Kolto containers.
This appearance takes place only a very short time before Republic characters enter the same location in order to free the duo from the Sith and attempt to save the Kolto.
If you don’t recognise Lord Tarnux, he was the Sith Lord that you defeat at the Docks on Mek-Sha at the end of the “Race to Refuel” quest, which takes place during the Republic storyline on Onslaught.

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