Ring of the Champion (5e Equipment)
From D&D Wiki
Ring, rare (requires attunement)
A brilliant silver ring created for a champion long ago to heal them in battle, eventually corrupted by the souls of all those taken by their hand. While attuned to this ring, when you are healed by any effect, you may roll hit dice to heal as well as if you had taken a short rest.
Curse. The first time you drop to zero hit points, the ring permanently changes to a dull grey. You can no longer heal by magical means. If the ring is removed while attuned, you drop to 0 hit points and fail a death saving throw every round. Replacing the ring will bring you back to 1 hit point. This curse can only be removed with a remove curse spell or another similar spell/effect.