Captaqin Marck, who is hiding behind a rock between the two Ember-Eye camps south of Koeglin Lighthouse, tells the Vestige all of his crew have been captured by Captain Angarthal, the cruelest slaver in the Azurian Sea and now in Iliac Bay. The ship hit the rocks as the lighthouse signal was out. They took most of the crew up the beach, but Salach, Lidenar and Ozor are still there, help freeing them and it will be worth the while.
After some more conversation, (optional), head to the camps to find and release Lidenar and Salach. Ozor is held captive on the pirateship, The Bloody Scupper and after releasing him, find the slaver captain. He's below deck with one of his guards. Attack and kill him, then return to Captain Marck on the beach.
All three crewmembers are with the captain, relieved for being released. Speak to Captain Marck to complete the quest. He asks the Vestige if heading that way, to look out for the rest of his crew who were marched off to the east.