Snake Pair: Ouroboros (蛇双・ウロボロス Jasō: Uroborosu, localized as Geminus Anguium: Ouroboros) is an Arch-Enemy Event Weapon in the shape of a black snake head attached to a never-ending chain. It is wielded by Hazama, previously by Yūki Terumi and Kazuma Kval.
The Ouroboros is the symbol of a serpent, or less-commonly a dragon, eating its own tail, personifying the eternal cycle of life and death, as well as infinity itself. It is believed that this Arch-Enemy can directly attack the mind and psyche of the victim by amplifying a victim's emotional vulnerabilities. Hazama uses this ability once in Continuum Shift, using it to unlock Tager's memories of the incident in the Seventh Agency. For use of combat, Hazama can use Ouroboros to zoom across the battlefield or reel himself or his enemy closer to attack. He can zoom forwards, diagonally, and also shoot Ouroboros straight up.
Ouroboros is also known as the symbol of alchemy, quite likely alluding to it being used in creation of the weapon, as well as its users (Kazuma and Hazama).