Argularragh was a massive dragon, even by dragon standards.
Argularragh was the ruler of the castle of Argul, in Eskorn, where it lorded over a commune of dragonborn slaves. However, one day Argularragh simply vanished without a trace. Most of the other Eskornar dragon lords believed Argularragh was killed by a rival during a sea battle and its body was lost in the waters, but a few of them believed that Argularragh was either trapped inside a magical item, or that the dragon learned how to change shape and went to live its remaining days as a member of another race. The few individuals who believed this tale, also believed Argularragh was still alive as of 1479 DR.