Possibly not a cursed item, per se, but definitely an evil one. This appears as a wide, and beautifully carved leather belt. It will radiate magic, if tested for. This belt will shrink or grow to fit any wearer.
A person wearing this belt regenerates any physical damage they may receive at a rate of 1 HP per minute, so long as there are living beings within 1000 feet. The belt will siphon off Hit Points from living enemies first, then from strangers, and then from friends and loved ones, in that order. The victim(s) will lose 1 HP per minute, as if taking some sort of internal damage. Animals, undead, and mindless creatures are unaffected.
What's more, any illness or poison exposure upon the wearer gets randomly pushed off onto someone else within 1000 feet, in the same order as damage from physical attacks, vanishing from within the wearer, and appearing in the victim. In this case, the victim of this transference is allowed a Saving Throw; if successful, the power bounces off them, and moves on to someone else. If everyone within a 1000 feet makes their Saving Throw, the wearer is stuck with the poison or disease, until someone new comes within range, and the belt tries again. After the first time this happens, the belt can no longer be removed through any normal means, requiring a Remove Curse of high level to allow it to be unbuckled and taken off.
If the wearer is killed while wearing the belt, it can be removed easily, but if it remains on them, and people come within 1000 feet, the wearer will eventually regenerate enough points to return from the dead.
Optional: It may be interesting for the GM to have this belt on some long-dead, but once powerful wizard or warrior, in a forgotten crypt somewhere, who begins to regenerate as soon as the players get close, doing damage to them bit by bit.