1. The Ring of Mediocrity
The Ring of Mediocrity adjusts all of the wearer's stats are changed to their average (add all together, divide by number of stats, answer is the new character's new stats while they wear the ring). This ring also changes the wearer's appearance factors to be average as well. This makes the wearer painfully indistinct, and hard to describe. People who meet the wearer will have almost nothing to grab onto to describe them.
2. The Ring of Lemures
The Ring of Lemures (named for the incredibly low ranked demon/devil that resembles a person made of melted wax) adjusts all of the wearer's numerical stats to match their lowest stat. This is a great cursed item to afflict min/max character builders, as it turns all of their stats into dump stats. A non-cursed version could be used to reign in the powers of a superhuman or metahuman being, allowing them to better hide among mortals.
3. The Ring Excelsior
The Ring Excelsior adjusts off of the wearer's numerical stats to match their highest stat, making the character dramatically more powerful, especially in the hands of a power gamer. A dangerous player will seek out abilities and items that boost a single stat, and then use this ring to make themselves staggeringly powerful.