Here's a twisted little magical artifact I found buried in my old hard drive. It should be compatible with just about any OSR style rules, although you may have to do a bit of tweaking depending on your system of choice.
This ancient staff is rumored to have once belonged to an insane magic-user - a demigod in his own right, if the legends are true - bent on dominating all mankind. He toiled for decades to create a staff that would further his goals, and once his task was complete his mind finally snapped. Nobody knows for certain what became of him after that, but his staff still exists today. It may be that it has changed hands countless times throughout the centuries, or perhaps it has just been hidden away, buried in some dark tomb awaiting its first owner.
The staff itself is fashioned from an unnaturally textured and indestructible wood-like material. The shaft is a dark blue color, banded with thick sections of copper and silver. Gems adorn the metal, but they are small and dully colored. The headpiece of the staff is composed of an unbreakable silver-like sphere which sounds hollow when struck. When used as a melee weapon, the staff functions as a +3 weapon. While holding this staff the wielder is immune to any form of illusion or mental control, and their AC is improved by 3 points.
The staff's spellcasting powers are activated by striking the sphere, either with a fist or object or upon a hard surface, which produces a distinct and unnatural ringing sound. By doing this and expending a 1 charge, the user of this staff may create one of several different spell effects. The spells available are Antipathy/Sympathy, Charm Monster, Charm Person, Feeblemind, Geas, Hallucinatory Terrain, Irresistible Dance, Mirror Image, Phantasmal Force, or Project Image. These spells will be cast at the level of the user. The staff has 15 charges and will recuperate 2d4 charges per day.
This staff is a sentient object, functioning in much the same manner as a sentient sword, with an INT of 18. It has no set alignment and may be used by anyone. It seeks only to control and influence the minds of as many sentient beings as possible, and if deprived of this it will attempt to assert its will on the user, calling for influence checks. If the will of the staff prevails it will not just randomly use its powers. It will seek the most advantageous path to controlling as many people as possible, often through scheming and long term plans.
There is no known method of destroying this artifact The safest recourse is to bury it deep beneath the surface of the earth, seal it within a man-made structure, or to send it to the bottom of a large body of water. Otherwise, it will eventually seek out and call to its next owner through supernatural means such as visions, dreams, and omens.