Greater Doppelganger are a stronger version of doppelganger that are capable of casting spells. They will cast Mirror Image and Haste before attacking. They can be found on Labyrinth Level 2 of Durlag's Tower.
They will also appear on this level as Durlag Trollkiller and the rest of his family, Islanne, Kiel, and Fuernebol. They will randomly shapeshift between the different family members and possess all of the attributes of their currently selected form. They are able to cast Cure Light Wounds and will cast it upon themselves and their fellow greater doppelgangers multiple times.