Dissimortuum’s Cursed Mask
Wondrous item, rare
The dissimortuum’s mask is nigh indestructible. When the creature is destroyed, its mask usually survives and breaks free. On its own, the object emits a faint magical aura with mixed enchantment and necromantic properties. It is a tempting souvenir, but any humanoid or giant foolish enough to don the mask is immediately wracked by pain and takes 7 (2d6) necrotic damage. The creature must succeed on a DC 15 Wisdom saving throw or become dominated by the mask. The domination arrives slowly. The creature acts normally for a day or two, but then the creature notices periods of time that cannot be accounted for. During these unremembered times, the creature gathers the grisly components needed to build a new body for the dissimortuum. This process takes a week, after which the creature is freed from domination as the dissimortuum arises anew and dons its mask once more.
Source: Tome of Beasts 1 (2023 Edition) p. 106