Helm of Devil Command

This bulky, eyeless helmet is made for a Pit Fiend but magically resizes to fit the heads of other wearers.

While wearing the helm, you can see out of it as though you weren't wearing it. In addition, you know the exact location and type of all devils within 1,000 feet of you. You can telepathically communicate with a devil within range, or you can broadcast your thoughts to all devils within range. The devils receiving your broadcasted thoughts have no special means of replying to them.

The helm has 3 charges. As an action, you can expend 1 charge to cast Dominate Monster (save DC 21), which affects devils only. (The spell fails and the charge is wasted if you target any creature that's not a devil.) If a devil can see you when you cast this spell on it, the devil knows you tried to charm it. The helm regains all its charges 24 hours after its last charge is expended.

If you are not a devil, using the helm's Dominate Monster property in the Nine Hells has a 20 chance of attracting a Narzugon, which arrives on the back of a Nightmare mount in 1d4 hours. The narzugon tries to recover the helm, killing you if necessary to obtain it. If it gets the helm, the narzugon tries to deliver it to its infernal master.