The Dark Wall creates a magical barricade that blocks enemy projectiles for a short period of time. The size and duration of the wall is depended on the charge level before it was created. If it is fully charged, it will create a moveable personal shell around Nier instead. The shield does not stop melee attacks.
Unlike for other spells, the time does not slow down during the charge, making it almost impossible to create a high level wall in the heat of a battle. Once casted, Nier is not able to recreate another wall untill the first one has vanished. Since the low level walls are also immovable, the usage of the spell is very limited outside of a few specific situations.