The Hiironi irstat was the largest Tarasin community on Cularin. It was formed from twelve irstat that had all settled independently near Cloud Mountain. When Cloud Mountain revealed itself to be a volcano by erupting, the twelve irstat were decimated. The survivors banded together and moved further away from Cloud Mountain, forming the Hiironi irstat. Their name reflected this history—"Hiironi" in Tarasinese meant "different but together."

When Reidi Artom came to Cularin, she made contact with the Hiironi irstat, not realizing they had no power to speak for the Tarasin as a whole, though its size did mean it was a focal point for a number of tribes. Artom and her crew founded the town of Gadrin near the irstat.