Lillith's Flames Tattoo

Alter: While this tattoo is applied on your skin, you regain 1d10 hit points every 10 minutes, provided that you have at least 1 hit point. Once this tattoo has restored 150 hit points since you last finished a long rest, it can’t restore any more hit points until after you finish a long rest.
Additionally, whenever you are reduced to 0 hit points, each creature within a 10-foot radius of you must make on a DC 17 Dexterity saving throw, taking 4d10 fire damage on a failed save, or half as much damage on a successful one. You also instantly regain all your hit points and expend all your remaining Hit Die. Once this property of the tattoo is used, the tattoo loses all magical properties until 7 days have passed.

Attunement: yes
Materials/cost: Phoenix feather, ???
Placement: Torso
Rarity: Legendary
Produced by a special needle, this magic tattoo represents a magnificent being capable of rebirth.

The idea for this tattoo was initially a suggestion voiced by worried alchemists as a way to prevent further loss of life that stemmed from their occupation’s volatile experiments. The ability to regenerate health was helpful, but the chance to survive accidents week after week was even more of a benefit. Unfortunately, the costs involved with producing even a single one of these tattoos far outweighed the combined revenue of many of those whose lives were extinguished in their pursuit of magical and scientific breakthroughs. (Plus, Lillith wasn't all that keen to be seperated from her feathers).