Ring of Regeneration

Source: D&D 5.2 SRD Magic Items

Ring, Very Rare (Requires Attunement)

While wearing this ring, you regain 1d6 Hit Points every 10 minutes if you have at least 1 Hit Point. If you lose a body part, the ring causes the missing part to regrow and return to full functionality after 1d6 + 1 days if you have at least 1 Hit Point the whole time.