Crown of the Blood of the Martyr (5e Equipment)
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Wondrous item, legendary (requires attunement by a creature of good alignment)
A crown woven out of thorny twigs. Floats slightly above your head if worn while attuned. Can be used as a +2 holy symbol by clerics or paladins.
While attuned, if you deal damage to a creature, they take 1d4 piercing damage as a small thorn breaks from the crown and lodges into their skin. This thorn and the wound it creates cannot be healed by any means short of a Wish spell; while the thorn remains, the creature's maximum hit points are reduced by 1 and it takes 1 damage every minute from blood loss. Multiple thorns may attach themselves to a creature.