Source: Explorer's Guide to Wildemount

Ring, rare (requires attunement)

If you die while wearing this gray crystal ring, you vanish and reappear in an unoccupied space within 5 feet of the space you left (or the nearest unoccupied space). You have a number of hit points equal to 3d6 + your Constitution modifier. If your hit point maximum is lower than the number of hit points you regain, your hit point maximum rises to a similar amount. If you have any levels of exhaustion, reduce your level of exhaustion by 1. Once the ring is used, it turns to dust and is destroyed.