The Demon Key is one of two keys used to seal away Bahamut.
Satan lived on as the Demon Key, or in Cerberus's words, he was "resting in peace". Lucifer apparently succeeded him in the position of Hell's ruler. According to Cerberus, the Demon Key could be used in a succession crisis among the demons.
The Demon Key was watched over by Belzebuth.
Gilles de Rais devised a plan to revive Bahamut and bring about the end of the world. To this end, he convinced Belzebuth to create a half-demon/half-angel child from Belzebuth's own essence, and use the child as a bearer for both the God and Demon Keys.
This child was Amira. Gilles de Rais informed Amira that she needed the God Key in order to reunite with her mother Nicole in Helheim. After Amira stole the God Key, she did her best to reach Helheim until the gods forbid her from going there as she could bring about Bahamut's revival.
To remedy this, Gilles de Rais tricked Amira into going to Helheim using a false map that claimed she was heading to Prudisia, her mother's "true" location. Once she was at Helheim, Belzebuth and Gilles (under the guise of Belzebuth's attendant Martinet) informed Amira of her true origins and showed her Nicole, whose subsequent death drove Amira into despair, and her cries apparently summoned the Demon Key to her.
Once Amira had unwittingly absorbed the Demon Key she became the Transcendence Key. She was sacrificed to Bahamut by Belzebuth, who was revived through their permanent fusion.
According to Belzebuth, he had intended to replace Satan as the new ruler, and by having Amira absorb the Demon Key, Belzebuth had practically wiped Satan from existence.
|Objects||Alessand's dagger • Amira's compass • Amira's pendant • Bahamut's Talon • Barossa's dagger • Black Bible • Bounty Hunter's Bracer • Charioce XVII's bracelet • Demon Key • Dromos • El's ocarina • El's toy • Favaro's crossbow • God Key • Golem • Green Stone • Hoverboard • Maltet • Marginal Golem • Martinet's concoction • Nina's whip • Précieuse • Rita's antidotes • Rita's staff • Smoke Bomb • Transcendence Key|