In the Material Plane, Azartane is the old name of Zaradene. The name changed shortly after Azartane’s conquest by Haven in its push towards unifying Abanasinia. The dialect of Common spoken in Haven tended to turn “Azartane” into “Zaradene,” and over time the latter became the name of the town even for its natives. Clement I was a king of Azartane, considered one of the best.
In the Shadowfell, Azartane is a town that looks almost, but not quite, entirely unlike Zaradene. It is evidently populated by shadar-kai, such as Aka, a woman whose acquaintance Seth made in a dream. Seth has not explored the Shadowfell’s Azartane, which has a cold, deep aura to it.