ESU-S4xA/NU-017 Onyx

Technology and Combat Characteristics
The Onyx is the final version of the Diamondback under Jack Kendall's use, which granted it the loadout akin to that of a beast. Its primary weapons are a pair of claw-like blades, and its Thruster range has been increased to allow for near breakneck speeds in movement, namely with the side skirt booster pods. Being topped off with a NU METACOM System, the Onyx allows for Jack to fight at the same level as the BURST RAID System, without the danger of his machine going berserk. It was developed by Jack after losing against the LCR and the death of Lena, causing him to design it as lethal as possible.

Armaments
- Retractable Dual-Blade Gauntlet: The Onyx is equipped with a pair of razor sharp dual-blade gauntlets on each of its forearms. Originally meant for underwater units for their streamlined design, they were taken and modified by Jack Kendall to fit his fighting style. In the end, all four blades (two on each gauntlet) have been equipped with heated edges which enhance their cutting power, as well as a claw-like shape for extra ripping damage. When not in use, these gauntlets can be retracted back into their ports, or ejected as an improvised ranged weapon that shreds through armor.

- 80mm Autocannons: These shoulder-mounted Guns can provide suppressive fire if an enemy is too far away for the gauntlets to reach. They serve as an alternative to the Swarmfire Missile Silos. At mid-range, they sport a notable stopping power when put up against approaching machines. Their lack of accuracy further encourages their use when up close and personal with the enemy. Unlike the autocannons of the Diamondback, these weapons are concealed under an armored plate, facing both cannons outwards from the head unit. They can raise upwards and rotate on a 180° joint, allowing them to prevent hindering the Onyx's movement.

- Swarmfire Missile Silos: Four Swarmfire Missile Launchers are mounted on the rear booster pods, with two on the outer side of each pod. Due to their homing ability, they are able to be fired backwards and arc around at the targeted enemy, serving as a surprise attack. When not in use, the panels covering the panels close up, and the entire assembly can be purged if necessary.

- Custom Hunter: Developed from the Hunters of the Ruby Kingship, it has been designed with the purpose to kill instead of capture. By replacing the Stunlock Node and Claw with an Actuator Spike mechanism, the Onyx can fire the Hunter into an enemy unit, then use the Actuator Spike to destroy its internals. This weapon was designed by Jack himself, using the Diamondback's Actuator Knuckle as the base. When deployed, it is fired out from its mount, similar to the Kingship's. It is mounted on the back between the booster pods when not in use.

History
Created after the near-destruction of the Diamondback, the Onyx was built with one purpose in mind: to instill fear in the hearts of all who dare cross its path. The death of Lena Cassidy prompted Jack to transmit his anger into the weapons of the machine, trading out the more elegant and sleek parts of the Diamondback with a monstrous and brutal look.

The Onyx first made its debut in its attack on Neptune Base, where the entire surrounding city was nearly destroyed in Jack's search for the killer of his wife. After decimating nearly all of the Neptune Remnants' reserve forces, it would remain inactive until the closing hours of the Battle of Midnight Base. Jack would bring the Onyx in to assess the loss he had just incurred, in which he made quick work of a taunting Katherine Isakura.

The Onyx's final battle was days after the Garrisai Restoration Program, in which the combined forces of the Archangel, Excalibre, Firestorm, and Harbinger managed to defeat it and its subordinates. The Onyx was defeated by the Excalibre and later recovered for use by Ian Hunt as the Onyx Repair.

Trivia
- The Onyx took its name from the Onyx Blaster, a weapon from Terraria.

- The Onyx has a similar design (with sounds) as the Banshee.

- It also resembles the design of Barbatos Lupus and Barbatos Lupus Rex.