Captain Svadstar is the Dunmer leader of the slavers active on Firemoth Island. During the quest Broken Bonds, Naryu Virian marks him as her target as part of her work for the Morag Tong. You will only briefly encounter him aboard the Slaver Ship before Naryu strikes him down, so you won't actually get a chance to interact with him. His only dialogue is "Intruder in the hold! Someone put out that fire while I deal with this flea!"