The Deepwater Harpoon Quest
1. Go to the Temple of Marr in Freeport.
2. Hail Serna Tasknon and learn about Sentry Xyrinn.
3. Recieve a potion bottle.
4. Bring the bottle to all the 8 guards in alphabetical order. The guards and the order are as follows: ANDLIN (Walks around outside wall); BORIS (Downstairs stationary); GALLIUS (Outside by front door); JANEAL (Downstairs stationary); MEIGHAN (Outside by front door); THEO (Patrols inside on upper levels); WARREN (Patrols inside on lower levels); XYRINN (final sentry in OoT -7000 -1000). If your faction is not high enough you can't get the bottle.
5. When you give it to the Warren he will tell you that she went to the Sisterhood of Erolisi. The sisters will tell you she is either dead or stranded on a nearby island.
6. Go to the island where she is stranded (-7000 -1000) and give the bottle to her. She will give it back to you to take back to the temple, after which you will be done. If you help kill all of the spectres and other undead that he was going to kill and then give him the potion, he will stand there for a while and then drop the Deepwater Harpoon.