Amulet of False Justice

This necklace  a round, glowing sapphire on which a single eye is inscribed. Once attuned to a creature, that creature cannot un-attune with the amulet or remove the amulet until it is destroyed, or they die. Attempting to remove the amulet by force causes it to tighten around the creature's neck dealing 1d4 piercing damage.

A creature wearing the amulet gains a +10 enhancement bonus to their base land speed and may attack 1 additional time when using the attack action. This extra attack is in addition to class features that grant extra attacks if any. 

Curse: False Justice

The attuned creature has disadvantage on all Wisdom saving throws except fear effects. Any time the attuned creature fails a saving throw against fear, they must also make a DC 15 Constitution saving throw. On a success, the eye inscription cracks, and the DC for future saves reduces by 5. If the creature fails the saving throw, it spends its next turn attacking itself with all available attacks against its own AC. If the creature would be knocked unconscious by its own attacks in this way, it will instead drop its weapons (if any), and rips out its eyes before laughing maniacally and falling dead. 

If the eye inscription cracks three times, the amulet breaks, losing all properties permanently. A successful "Remove Curse" spell will crack the eye inscription once. If the Amulet of Fasle Justice would be destroyed in this way, it instead becomes an Amulet of Concentration.

Notes: Disadvantage: Wisdom Saving Throws, creature proficient with martial weapons, Damage, Buff, Movement, Combat, Cursed, Necklace, Jewelry