The dragon known as Ebondeath, is an ancient black dragon with a long existence, it's root lost in the depths of time. The Dragon disappeared for millenia until 631 DR when Ebondeath emerged from the Mere of Dead Men in the Sword Coast North. It made the Uthtower it's lair and raided the Sword Coast from there.
Slain by adventurers he reappeared in 922 DR, as a dracolich worshipped by a draconic cult. This was destroyed and the dragon driven back into the mere by a coalition of Neverwinter, Baldurs Gate and Waterdeep. It was not seen again until The Leilon...Some? found Ularan Mortus imprisoned in a battle of wills with the spirit of Ebondeath, deep in the Uthtower.