Rebellion

Rebellion is one of the three sacred spirit treasures artifact.

Overview
It is a sentient weapon that can possess objects and people, drawing upon negatives emotions to strengthen itself. However, it comes at the cost of the user's life. It appears to be amorphous in appearance, only having disturbing eyes and mouths and a sinister aura as a mainstay feature.

Spoil Arc
The location of Rebellion was offered as a reward for the successful capture of the UMA Past.

Unrepair Arc
After Juiz, Nico Vorgeil and Phil successfully captured UMA Past, Apocalypse rewarded the Union by pointing out the location of Rebellion as being in Egypt.

Ragnarok Arc
During the stand off between Sun and the Negators, Victor has Rebellion possess Juiz's sword so she can use her hatred against God to empower it. However, rather than that, she instead fuels it with her comrades' bitter regrets, her own powerlessness, and her rage for what God did to Victor for so long. After she dies, Victor, fueled by the loss of her love, has Rebellion possess him, launching a beam attack that barely holds Sun back long enough for Fuuko to loop. It and Victor then go on to fight as many Suns as they can before the world is destroyed.

Trivia

 * Rebellion's name may be a reference to Dante's sword named Rebellion from the Devil May Cry series.