Mount Esterrin is the highest peak in Arin that is not part of the Thair Mountains. It sits on the eastern side of Lake Varn, rising from the center of the great plain. For many years, it was home to one of the strongholds maintained by Keraptis, who was the power behind the throne of several kings of Arin. Its fastness was breached only once, by a group of adventurers led by Zorg, who had come seeking several powerful magical artifacts that had been stolen by Keraptis.
Mt. Esterrin was once called "White Plume Mountain", and was thought by many to be an active volcano due to the large amount of white smoke that rose from its summit like a plume. After the Wars of Arin were concluded, it was discovered that the smoke was artificially created by Keraptis to keep away the curious. Some rumors hold that the mountain itself is not a natural mountain, but was built by Keraptis through the use of mighty magic, although there are few alive today who could confirm or deny this.