Gathwen is a Bosmer who comes running for help around the Temple of the Mourning Springs. She and her master, Rurelion, were shipwrecked, and they came to the temple when they heard that the water never ran dry, referring to the Mourning Stones.
Gathwen and the Vestige enter the temple to find Rurelion. They battle Rurelion, who is being controlled. She will sacrifice herself to seal Uldor. The Vestige has the option to either seal Rurelion or Gathwen inside the tomb. If Rurelion is chosen, then she will get the Mourning Stone. She will swear that she will free Rurelion from Uldor eventually.
If Gathwen is chosen to live, then she will offer to help the Vestige battle the Sea Vipers.