In order to summon the banshees, you must first locate and build 3 Minotaur statues before an unseen timer runs out. If you do not build them all in time, the statues will smashes themselves and you will need to build those that have smashed again. Upon building all three, a white mist will form around the maze, which will also send your character flying back as banshees start to fly around. When this happens, the Crone of the Maze spawns, along with the Banshees. Until you smash her, Banshees will continue to spawn. The Crone of the Maze can also summon Banshees herself.
- Banshees currently are the best way to farm for minifigure achievements that require you to smash witches.