Domino Project

Interstellar Era
The Domino series of Garrisai, most notably the Domino III, was a prototype mobile weapon designed to house a portable version of the Solar Cannon. While the Catalyst was designed for the exact same purpose, it was seldom maneuverable from having tank treads instead of legs, an asymmetrical design that often caused it to lose control, and required a separate "core base" that was the one charging its laser. These three problems (among others) were what the Domino series aimed to solve. This, along with the experimental ATS that allowed for long-range combat for the first time, would be seen improved in all three units.

Evolution
The first two Dominos were also the first to house a twin-drive system. Since the Solar Cannon required such a high amount of power to use, and the only way of powering it was through Ichor Cores, two Fusion Drives were needed in order to allow continued operation after firing.

The Domino I started out as a standard-frame Garrisai with an externally held turret, that would fire the laser when connected to a power tube. This design was solid at first, but continued operation showed that deployment of the weapon required multiple Garrisai to do. This unnecessary amount of personnel needed was solved in the Domino II.

The cannon was eventually proposed to be mounted in the chest, as it allowed the machine to maintain its center of gravity without the need to carry around the weapon and set it up. It also allowed for the cannon to "spin up" similar to how it did on the Catalyst. This weapon was shown in the Domino II. However, a new problem arose in this machine. The two drives could not spin up fast enough to power the cannon with sufficient energy, as the room needed to implement the cannon came at the sacrifice of a smaller twin-drive system. The drives often overheated during their spin-up sequence, causing this unit to nearly melt.

Parallel Operation between the drives was a long-standing problem with the Domino Series as well, since there would be times when the drives would not spin up at the exact same speeds, causing the weapon to incorrectly fire.

The Third Unit, Domino III, was a complete re-tooling of the Domino II's T-DS as it relocated them to the back of the Garrisai. This allowed the drives to vent, as well as return them to a size sufficient enough to fire the laser continuously. The unit worked like a charm during testing, and was even sent out to defend the City in Polaris in 2431.

This was when the general unluckiness of the Domino Program hit its peak. During this defense, the Domino was able to successfully shoot down several CSs during the attack. Paired with the Harbinger GTs also stationed there, they seemed to be on track to victory. But when the machine fired for its seventh time, it was approached by an Interstellar mecha, which knocked it down during its sequence.

The laser skimmed the side of the CS it was aiming at while it continued to fire into the sky, and the Domino III fell to the ground. The exposed TDS became unstable as they were still spinning when the machine fell, causing them to spontaneously destabilize and release an explosion the size of an atomic blast. Polaris City (except Guardia Seven, which was shielded by the TERRA) was leveled in seconds. This catastrophe became known as the Domino Incident, and the previous two units were swept back into storage in attempts to hide any evidence of the project (similar to the Nightwatch Incident).

The machine did get a saving grace in the form of the Domino IV, which replaced the Solar Cannon design with a standard 500mm Railgun. This one fired conventional "solid" rounds as to limit the risk of an explosion.

Post-Interstellar Era/DUALITY Side-Story
When the minds at the DTRO discovered evidence of the Domino Project, they proposed a complete overhaul of the SCO design. Orchestrated as the Domino Revive Project, blueprints were designed for a Head-Mounted Cannon instead of a Chest-Mounted one. This was in order to conceal the Twin Drives, while keeping the machine's center of balance as a fixed weapon. However, the design of the reactors had seldom changed, meaning that the parallel charge-up time was still a problem. Regardless, the development continued, as a weapon capable of downing Celestial Striders would certainly do far worse when in Anti-Garrisai combat.

This was when a designer on the Domino Revive Project named Samantha Jenkins noticed that the Arcandy Project (that was going on at the same time) would be perfect in supplying sufficient energy for the cannon. She proposed this idea, along with some of her own for minor changes to the project, to her advisors. However, she was only met with dismissal as they did not believe that the new designs were even possible.

During the fall of the NDRC, Jenkins stole the blueprint data for the Domino Revive Project, as well as a mass-production Arcandy Compact Reactor. She took these designs to the UNI alone, as she knew one of her companions (Marie Winhart) would listen to her. Marie, after being approached with the projects, eventually agreed to help her friend build this design. Jenkins herself was also accepted into the UNI for her contributions. This was Marie's payback for Sam.

Along with the child prodigy Connor Holland, an expert in Garrisai tech for someone his age, Sam built the Domino machine that used an Arcandy Reactor. When it was finished, the Domino was hardly combat-ready, but still capable of firing the weapon for a reasonable amount of time. It became known as the fearsome Solar Eclipse, which would put the UNI with one of the most powerful weapons ever developed.

Harbinger Uprising Era
By the events of Harbinger-LEGACY, the Solar Eclipse had been properly outfitted with heatproof armor, lockdown mechanisms, and a rather flamboyant head design conjured by Sam herself. The machine almost never left the UNI's fortress, Guardia 7, similar to the Terra that had been left there as a shield generator. Assisted by the Terra for protection, it would fire down upon any machine that didn't have clearance with the UNI.

It was first introduced when Alex, Dom, and Cece approach the base, when a massive laser blast fires down from the base near meters from where they stood. This laser blast turned out to the the Eclipse mounted in a turret-based shell. To the rest of the Decholonian people, the weapon became known as the "Hand of God" by any of the splinter groups who dared approach the base.

Despite having limited competition, numerous reports from smaller factions have stated that their patrols had been completely wiped out at the hands of a "giant green laser." The machine would eventually be released from its shell and fight in active combat, piloted by Sam herself.