Although most derro of the Darklands live in smaller communities, three larger settlements do exit among the twisted tunnels of Nar-Voth. The largest of these is Corgunbier, a series of maze-like tunnels located directly under the Taldan city of Cassomir. Countless secret passageways connect the two population centers, providing a simple way for the derro to collect subjects on whom to perform their torturous experiments. Corgunbier is home to almost two thousand derro and over a thousand of their mongrelman slaves, and is ruled by a trio of derro savants known as the Ecliptic Triad.