Been thinking about cursed magic rings lately and thought I'd share some of the ones I've come up with.
Ring of Appearances - 3/Day wear can cast disguise self; after each casting, base 10% chance + 5% per casting, one aspect remains disguised permanently.
Ring of Life - 3/Day wearer can cast cure light wounds; wearer leaves dead footprints anywhere they walk on grass; cannot wear organic clothing or armor; significant negative reaction from any good aligned healer and/or denizen of the forest.
Ring of Raging Change - 1/Day gives the wearer the Barbarian Rage ability; must enter into mortal combat at least once a day, everyday that the wearer does not enter into mortal combat, the wearer changes one physical aspect to that of the ring's previous owner.
Ring of Random Blinking - +1 AC to the wearer; if the wearer is hit by an attack, the ring blinks the wearer away up to 100' (d100) in a random direction (use a d8 on a grid, d6 on a hex or d12 for no battle mat) - if the space is occupied, both occupants take d10 damage and are knocked prone to an adjacent space; if space is occupied by a solid object (tree, wall, etc.), wearer takes d10 damage and blinks to a new space.
Ring of Scrying - 3/Day wearer can cast scrying; has base 50% chance + 10% per use per month to summon the closest Beholder, who now hates the caster. Beholder arrives in whatever time it takes to travel however it chooses to the caster and knows casters whereabouts at all times. Beholder can choose to see through the casters eyes up until the Beholder and caster first see each other in person.
Ring of Sliding - Wearer can cast teleport as the spell; each time the ring is used, it uses 1d4 charges from a nearby charged magical item; if no charged items are within 100', ring uses 1d6 spell levels from a spell caster; if no spell caster is within 100', ring uses 1d8 hp from wearer; has 5% base chance and +5% change per use each day to summon 1d4 Invisible Stalkers to attack wearer.
Ring of Thunderous Bolts - 3/Day wearer can cast Lightning Bolt at character level, though the bolt is always centered on the caster, extending equal distance in each direction; wearer is immune to electrical damage but takes X2 damage from fire and cold.