The Slave Crown was made by Kefka using Magitek technology. He created it so that he could directly control the actions of whoever used it. He had Terra wear it and ordered her to burn fifty of the finest Imperial soldiers, which she did. She was later ordered to infiltrate Narshe in order to investigate the appearance of 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 the party 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. However, the residual effects gave 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. Over the course of the game, these effects wear off and Terra returns to normal.
Despite being a fairly important plot device Terra's Slave Crown is the only one ever seen or mentioned in the game. The reason why more of them were not put into use is unknown. Arvis referred to it as "a Slave Crown" in a context that he was familiar with its effects and Terra was unusually strong to remember her name so soon after it was removed, indicating there were others.
- In Dissidia Final Fantasy, there exists a unique Accessory called "Puppeteer's Wheel," which grants a large boost to 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 same 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.