Viper

"Ballistics for which you can choose the trajectory: Viper."

- Shiori Usami about Viper.

Viper is a Gunner Trigger.

Appearance
Viper leaves a luminous trail in its wake, and can be recognized by the sharp angles it performs as its trajectory changes. When set to travel in a straight line, it is virtually indistinguishable from other Gunner Triggers; upon impact, this would also apply if the user's trion level is not taken into account.

Overview
The origins of this Trigger are unknown. It was initially used exclusively in trion cube form, until firearms were invented.

Abilities
Viper is one of the mid-ranged options available to Border agents, which can be fired as a trion cube or through a firearm. It is slightly less powerful than Asteroid, as part of the trion allocated to the bullet is spent on its signature ability to travel along a predetermined trajectory, which grants it even more complex flight paths than Hound. Although the number of patterns available is theoretically infinite, due to Viper being the most difficult Gunner Trigger to master, the vast majority of users learn only a few useful patterns. One of the most common consists in having the bullets move in a straight line before fanning out in multiple directions. This can be done to quickly target multiple opponents unpredictably, shoot around corners, and feint going after one target only to catch another off-guard. Another widespread application of Viper sees the bullets spreading out and then converging on the target from multiple angles, allowing the user to circumvent the enemy's shield instead of breaking through it.

A handful of Border agents are capable of creating new flight paths in real-time, a skill which requires advanced visualization and keen spatial awareness. This ability makes their shots extremely difficult to anticipate and counter, on top of rendering most stationary obstacles useless as shelter against their fire; they may even exploit an obstructed line of fire by curving the flight path of the projectiles out of sight so that the opponent will misestimate their point of origin. Viper users capable of coming up with trajectories on the spot can target multiple opponents with the same bullet, so that if a bullet fails to hit its first target it may converge with the second. This can be due to the first target dodging so the bullets curve unexpectedly, or the volley following a plethora of different trajectories so that at least some will miss the first target and thus be able to continue along their path. These bullets may be set to return toward the user after luring other opponents into believing that firing the volley left them vulnerable to attacks.

As a Gunner Trigger, Viper is less powerful than Attacker Triggers in normal circumstances and consumes more trion than the latter. The higher the trion amount of the user, the more of it can be allocated to its three basic parameters, enhancing its performance. A safety mechanism is in place so that, should a bullet collide with a flesh and blood body, the owner will be knocked out from the pain and impact, without suffering any penetrating trauma.

Users
See also: Viper Users

With a mere eight known users, Viper is the most unpopular Gunner Trigger. Among its users, three fire it in trion cube form, three through an assault rifle, and two through at least one handgun. Rei Nasu, Kōhei Izumi and Hyuse are the only agents capable of coming up with new trajectories on the spot. Viper is also used by an unknown number of trainees, and possibly by agents who do not take part in rank wars.

Trivia

 * Like other Gunner Triggers, Viper may have been named after a missile, the AGM-80 Viper, whose system offered fire-and-forget performance. Alternatively, it may be derived from a rocket, the FGR-17 Viper.
 * The viper is a family of venomous snakes. Snakes have many vertebrae which allow for increased flexibility, which is similar to how this Trigger is flexible in changing trajectory.
 * The three users capable of creating new flight paths on the spot fire Viper in trion cube form and are the only ones to do so.