Blade of Broken Mirrors

The Blade of Broken Mirrors is a dagger and one of the Arms of the Betrayers created by Tharizdun from the soul of a Glabrezu named Ragazuu. As a sentient weapon, it has a Chaotic Evil alignment and can communicate with its wielder telepathically. Similar to a a Vestige of Divergence, the Blade of Broken Mirrors progresses through various stages as it is wielded and gains new properties, including giving its wielder the ability to assume the appearance of a slain foe, cast various spells, and turn invisible.

Description
The Blade of Broken Mirrors is a dagger made of jagged stone. The blade is scribed with a maze-like pattern that has no beginning or end. The dagger was made from the soul of the Glabrezu Ragazuu, who whispers ideas of revolution to its wielder, learning their principals and encouraging them to reckless action.

Properties
Like all Arms of the Betrayers, it progresses through stages—dormant, awakened, and exalted—and becomes progressively more powerful as it is wielded. Each stage has all the properties of the previous stages.

Dormant state

 * One random minor beneficial property and one random minor detrimental property.
 * The wielder knows Abyssal.
 * The wielder has a +1 bonus to attack and damage rolls made with this weapon.
 * If used to make a ranged attack, the weapon immediately returns to the wielder.
 * As an action while holding the blade, the wielder may take the form of any humanoid creature killed with this weapon. All statistics except for size remain the same, and any equipment worn or carried by the wielder is unchanged. All forms remembered by the blade are lost when a new creature attunes to it.

Awakened state

 * One additional random minor beneficial property and one additional random minor detrimental property.
 * The bonus to attack and damage rolls increases to +2.
 * The wielder may cast the following spells once until the next dawn with a DC 15 save: Fabricate, Hallucinatory Terrain, Major Image, and Phantasmal Killer.

Exalted state

 * One random major beneficial property.
 * The bonus to attack and damage rolls increases to +3.
 * The DC for the spells becomes 17.
 * As an action while holding the dagger, the wielder can turn invisible and remains invisible until they put down the dagger, make an attack, cast a spell that forces the target to make a saving throw or use a bonus action to become visible again.