The Slave Crown was made by Kefka using Magitek technology to directly control the wearer's actions. He had Terra wear it and ordered her to burn fifty of the finest Imperial soldiers, which she did. She is later ordered to infiltrate Narshe to investigate the appearance Valigarmanda, a recently dug up esper. Biggs and Wedge, two Imperial soldiers, accompany her and Biggs questions Terra's loyalty, but Wedge points out the Slave Crown and assures Biggs she would do what they say. When they reach the esper it presumably kills Biggs and Wedge and disrupts the Slave Crown's hold. The Crown is later seen in Arvis's possession, a Returner living in Narshe, and it is assumed he destroys it. The residual effects give Terra amnesia of most of her life until some time later, and it is implied by General Leo that her emotions and feelings were dampened as well. These effects eventually wear off and Terra returns to normal.
Terra's Slave Crown is the only one ever seen or mentioned in the game and the reason why more of them were not put into use is unknown. Arvis refers to it as "a Slave Crown" in a context he was familiar with its effects and Terra being unusually strong to remember her name so soon after it was removed, indicating there are others.
- Dissidia Final Fantasy has a unique accessory called "Puppeteer's Wheel," which boosts the amount of time one can sustain EX Mode. Terra wears the accessory in Destiny Odyssey III when fought as an enemy, paralleling the Empire's control of her using the device in Final Fantasy VI. Also, in Dissidia 012 Final Fantasy some cutscenes show a lack of light reflection in her eyes, a gimmick commonly used in Japanese character designs to indicate either possession, hypnosis or trance.