Ring of Regeneration
Ring, very rare (requires attunement)
While wearing this ring, you regain dice:1d6|noform|noparens|avg (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 dice:1d6+1|noform|noparens|avg (1d6 + 1) days if you have at least 1 Hit Point the whole time.
Source: Dungeon Master’s Guide (2024) p. 294. Available in the SRD and the Free Rules (2024)