Azakaal Empire
The Azakaal Empire was the last great kingdom of the Old Gods' servitor races, surviving for 2500 years into the early First Age. Ruled by the Sith'aal, it covered almost all of northern Zarkhir as well as parts of southern Atharys and Karnathas.
The empire had been in slow decline since the War of the Elders and was ravaged by some great beast (possibly the Tarrasque) in its last years. Eventually the empire gave way to the ascendancy of the Sylvari, Runir, and humanity.