To make use of the Sack's powers its owner must plunge their hand into the bag's orifice as they speak the command word required to activate its magic. The interior of the bag is filled with a thick, blood-warm liquid, a portion of which, as the command word is spoken, congeals into a living eye that floats into the owner's grasp. Depending on the command word spoken, the eye produced can have one of the following aspects:
- Regenerative Organ - This organ is a fully functional human eye. If placed within an empty eye socket within five rounds it instantly bonds itself to its new host's body, becoming a fully functional eye. The newly installed eye has a red iris and a slight cast, which does not affect vision, but does present a somewhat daunting appearance. The recipient suffers a one rank penalty on initial impressions based on appearance.
- Undead Watcher - This eye is a bit small, with a dead gray iris and bloodshot sclera. The Sack's owner can place this eye anywhere. With a full round's concentration they can shift their gaze to see what the Undead Watcher can see. The Undead Watcher is static, and easily destroyed if noticed, but its small size makes it difficult to spot.
- Parasitic Eye - This eye has a golden-brown iris with a vertical slit pupil. Gooey tendrils dangle from its bulk, dripping noxious, thick liquid. The Sack's owner can attach this eye to living flesh, where it bonds instantly. The eye provides no benefit to its host, but the owner can, with a round of concentration, shift their gaze to see what the Parasitic Eye sees. Damage to the Parasitic Eye is suffered in equal measure by the host. Only a Good damage cut will remove the entire Eye from the host's body. Any fragment remaining will regrow to a complete eye in 2d6 days.