Lord Grathan is a rogue Sith and mad scientist hated by many in the Empire, especially the Dark Council. He conducts many crazy experiments in his estate, where he lives with his wife Cellvanta and his son Beelzlit.
All four player characters are sent to his estate to deal with him in one way or another: Bounty Hunters deal with Vereta Fraabaal, one of his apprentices; Sith Inquisitors break into the estate to steal a prototype while Imperial Agents kill a rebel he is sheltering. Finally, Sith Warriors are sent by Darth Baras to deal with him directly: dark sided Warriors follow Baras's orders to kill Beelzlit (and his mother along with him), while light sided Warriors take up Cellvanta's offer to let Beelzlit replace his father and finish off the man himself.