Demon’s Metamorphosis

Armor (any), very rare (requires attunement)

This magic armor is carved from the hide of an Abyssal fiend and enchanted with corrupting magic.

Aura of Malevolence. Whenever another creature within 10 feet of you makes a saving throw while you re wearing this armor, the creature must roll a d4 and subtract the number rolled from the saving throw.

Metamorphosis. While you re wearing this armor, you can use an action to transform into a Demon you have seen before with a challenge rating equal to or lower than half your level for 1 minute. The transformation functions as the polymorph spell, except that your demonic form is constantly at risk of running amok. At the start of each of your turns while transformed, you must make a Wisdom saving throw (DC 10 + the demon’s challenge rating). On a failed save, you momentarily lose yourself; your personality and alignment are replaced with that of the demon’s and you must act in accordance to the demon’s nature until the start of your next turn. Once used, this property can’t be used again until the next dawn.