The Hazel Realm, or Coll Regalis, was one of the five royal houses of black squirrels. This one in particular was protected only by the wisdom of its queen, who wore a bronze hazelnut necklace. The hazel is regarded as the fount of all knowledge, and Coll Regalis was second only to Greenreach in its importance.
The last ruler of the Hazel Realm was Lady Ninnia, the mother of Ysabelle. It was destroyed by the bat army on Aldertide (since then the holiday has not been celebrated by the squirrels due to the association).