Oosith was an aboleth lieutenant of the Kraken’s cult in Yartar, where he helped coordinate the kidnapping of multiple nobles with the aid of Lady Atalia.
When Lady Atalia attempted to redirect the Seekers into killing Oosith to replace him as lieutenant, he anticipated her betrayal. Disguised as a human wizard, he revealed her treachery to the group, then emerged in his true form and triggered a deadly underwater battle. He was killed by former Seeker Korosu. Red took one of his teeth as a trophy, but it disintegrated within a month.