Bloody Cloak (3.5e Equipment)
From D&D Wiki
Bloody Cloak: A very fine dark red with black trim and a gold clasp.
When worn, this cloak constricts around its wearer. Every round, the wearer must make a DC 20 Will save; If they succeed, the cloak will release its grip and fall off the wearer, if the save is failed by 10 or more, the current hp of the wearer is halved. This item has an evil aura.
When worn, a successful knowledge (arcana) check, DC 40 will make it safe to wear until it's taken off again, but it will still attack anyone else who tries to wear it.