|“||I'm burnin' for a beatdown something fierce!||„|
English Website Description
Viper is an adept who keeps watch over Sumeragi’s chemical plant complex. His septimal power, known as Explosion, gives him the ability to compress a large amount of thermal energy into small spheres that explode on impact. He can also engulf his body in flames to deliver extremely deadly attacks. Viper was once a notorious gang leader, but once he became infatuated with Lumen’s voice, he quickly found himself signing up for Sumeragi’s private army. The Glaive which holds his septimal power is called the Lord of Fire. 
Viper is a teenage boy with red eyes and spiky red hair, as well as a ponytail. He wears a black double breasted jacket with gold highlights, and a white shirt underneath that. He wears checkered cargo pants and black boots. He also wears sliver earrings.
Representing the sin wrath, Viper is hot-headed, loud, and vulgar. His most notable attributes are his incredibly short temper and highly defensive attitude, the slightly tease able to send him into a whirlwind of fury. Once, he savagely beat one of his own gang members for making fun of him. However, when he isn't consumed by rage, Viper can be surprisingly calm and aloof, showing a general interest in nothing in particular and is very dismissive about everything in general.
It's revealed in Justice Rage that Viper generally dislikes his septima, calling it meaningless, and saying he never asked for it. He also holds some resentment against society, feeling discriminated against due to his septima, and fully acknowledging people only follow him out of fear, and often feels a general "emptiness".
Viper is also extremely infatuated with Joule, her being the sole reason he joined the Sumeragi Group, saying she is "cute" hooked up to machines, and that Nova promised to give her to him after Project Muse was finished.
Plot in Azure Striker Gunvolt
At some point in time prior to the events of the story, Viper is the infamous leader of an street gang known as Maiden Blood. After hearing the voice of Sumeragi Group's media icon Lumen, Viper falls madly in love with her songs to the point where he enlists in Sumeragi's private army.
Biochem Plant (Conflagration)
At the beginning of the story, the protagonist Gunvolt frees Lumen from her forced role as Sumeragi's sonar in their project to locate and capture adepts throughout the world.
When Gunvolt sets out on a resistance mission to place a bomb inside Sumeragi's biochemical plant, Sumeragi sends Viper on a mission to stop him. Viper meets Gunvolt near the plant reactor and reveals his rage towards Gunvolt for essentially abducting Lumen from Sumeragi; the two fight shortly afterwards. The battle here results in Viper's loss and death.
At some point after he is killed, Viper is resurrected by Sumeragi's necromancer, Elise. He, along with other resurrected Sumeragi adepts, await Gunvolt's arrival at Sumeragi's orbital space station, Firmament, to subdue him in his efforts to topple Sumeragi.
As anticipated, Gunvolt ascends an Earth-to-space elevator to Sumeragi's orbital space station, Firmament, on a mission to topple Sumeragi once and for all. During his ascension, the resurrections of fallen Sumeragi adepts appear to quash Gunvolt's mission. One such resurrection is of Viper, who ultimately meets his demise yet again.
Viper does not make any canonical appearances after this.
Powers and Abilities
Viper's septima, Explosion, allows him the ability to compress a large amount of thermal energy into small spheres that explode on impact
The boss fight with Viper is unique in that fire pillars stand at the sides of the screen, restricting movement within the boss arena as well as providing arena hazards for Gunvolt.
Viper's standard attack. Viper performs a quick sliding kick across the floor towards Gunvolt.
- At battle phase one, Viper may perform two slides consecutively. Beginning with battle phase two, Viper no longer performs consecutive slides.
- Viper will always follow-up this attack with his angry bombs or his unicorn drop. 
Viper's standard attack. Viper fires three explosives in an upward arc.
- The explosives can be detonated if they come into contact with Gunvolt's Flashfield or if Gunvolt shoots them with his bolt; the explosives leave lingering explosions in the spot where they were detonated.
- Viper will not proceed to his next attack until lingering explosions have dissipated. 
Viper begins using this attack at battle phase two onward. Viper first jumps towards the fire pillar farthest from him. He then performs a wall-kick towards the other fire pillar, shooting a three-way set of angry bombs towards the ground while he is mid-air. He performs a second wall-kick once he reaches the second pillar, shooting a two-way set of angry bombs towards the floor while he is mid-air. At the conclusion of this attack, Viper will perform a third wall-kick towards Gunvolt and kick him.
- Viper may follow-up or interrupt this attack with his volcanic axe attack or feint assault.
- If Gunvolt is in the way of any of Viper's jumps / wall-kicks, then Viper will kick him into a fire pillar and cancel this attack. 
Viper begins using this attack at battle phase two onward. Viper performs this attack as a follow-up or cancel to his unicorn drop. When Viper wall-kicks towards the ceiling in his unicorn drop attack sequence, he will disappear momentarily before performing a drop kick on Gunvolt. The drop kick's impact on the ground causes two bits of fiery debris to rise and fall on either side of Viper.
Viper begins using this attack at battle phase two onward. Viper performs this attack as a follow-up or cancel to his unicorn drop. When Viper reaches a fire pillar at any time during his unicorn drop attack sequence, he may jump towards Gunvolt and fire a three-way shot at him.
"Rays of searing heat / The sun returns all to ash / Beneath its wrathful gaze! Refulgence!"
Viper's special attack. Viper performs wall-kicks across the fire pillars until he reaches the top of the screen; whenever Viper makes contact with a fire pillar, two bits of fiery debris will drop onto the floor. He then fires several dozens of slow-moving fiery shots that radiate outward. He then proceeds to oscillate side-to-side in the air, firing slow-moving waves of three-way and two-way shots.
- Viper's design is based on a centaur as seen in his concept art for Azure Striker Gunvolt. His hind legs double as boosters that can fire explosives.
- The seven Sumeragi adepts are based on the seven deadly sins and an animal based on it. Viper represents Wrath and based on the Unicorn.
- Viper is one of two bosses available to fight in the Azure Striker Gunvolt demo. The other is Jota.
- It is heavily implied in the soundtrack Justice Rage that Viper has a lolita complex.
- This is even flat out stated by one of his former gang members, who quickly meets Viper's fury.
- ↑ 1.0 1.1 English Website Dossier
- Official Japanese Tweet Regarding Viper