The Event Weapon Dispossession Operation (事象兵器奪取作戦 Jishō Heiki Dasshu Sakusen, localized as Phenomena Weapon Dispossession Operation) was a major event that happened in 2193 AD in the 4th Hierarchical City "Naobi". It heavily involved both the Seventh Agency and the World Void Information Controlling Organization. Now, only two survivors of the event remain; Iron Tager and Azrael.
Due to an anonymous tip, Seventh Agency discovered the presence of the Arch-Enemy Event Weapon - Machine God: Nirvana buried deep within the Hierarchical City "Naobi", fearing that the Controlling Organization had also received the same news, Seventh Agency hired a mercenary troop to be sent to the ground level and excavate the Arch-Enemy. However, when the squad had excavated Nirvana, they encountered Controlling Organization soldiers and the two groups engaged in combat. Many lives were lost as Nirvana reactivated due to a small amount of energy left within it, and it attacked, killing several troops. To add to the hopelessness of the operation, Azrael appeared and wiped out every single combatant, with the exception of Tager, the commander of the squad, who had suffered a mortal wound from both Azrael and Nirvana. When Seventh Agency realized that the odds were stacked against them, they had Tager and Nirvana evacuated as soon as possible. It was from here that Tager's memories were wiped out after the life-saving surgery Kokonoe performed on him.
The aftermath of the event was somewhat devastating. Bullet, who belonged to the squad, has been searching answers for what happened during the event for the last 5 years since it happened. It is because of this that she is on the constant hunt for both Kokonoe and Relius Clover; two major players in the beginning of the event and its immediate consequences.
The majority of the details concerning the event are sketchy, due to multiple sources conflicting, such as the short story That which is inherited and comments dropped by Azrael in BlazBlue: Chronophantasma.