At least until the year 3E 426, Athyn Llethan was King, High Councillor and Lord of Morrowind. During the events of The Elder Scrolls III: Tribunal in 3E 427, he has just recently died and was succeeded by his grandnephew King Helseth, son of Barenziah. It is rumored that Athyn Llethan was grooming one of his nephews, Talen Vandas for the throne. However he died before he could ascend to the throne, which fell to Helseth Hlaalu instead. It is widely suspected that both Talen Vandas as well as King Athyn Llethan himself were murdered by the new king, but no proof has been found.
Athyn Llethan was the uncle of Queen Barenziah and thus the granduncle of his successor King Helseth Hlaalu. He was also uncle to Talen Vandas. He was married to Ravani Llethan and was a member of House Hlaalu.
Athyn Llethan during being king of Morrowind held the following title:
"Sovereign King Hlaalu Athyn Llethan, by the Grace of All Gods, King of Morrowind, Duke of Mournhold and Hlaalu Province; Defender of the People and the Law; Loyal Servant of the Empire"