Thurl was an Andorian chan or thaan, born in the early 24th century. A man of noble blood, he was briefly crowned as King of Greater Andoria, but abdicated shortly thereafter, turning the throne over to Collev in exchange for a generous payoff.
In 2365, following the death of Collev and his heir, Bregev, Thurl agreed to return from exile and reclaim the throne, in order to avert a civil war on Andor, per an agreement negotiated by Captain Jean-Luc Picard. However, Thurl was assassinated while swimming on Pacifica. Yevan convinced Picard to bring Thurl's body back to the Valley of Sorrows on Andor, where in accordance with royal tradition, Thurl's body was to be consumed by wild kritkraws. (TNG - Enterprise Logs short story: "The Captain and the King")