I couldn't miss the chance to practice my drawing!
Omicrons are a species of robotic lifeforms originally inhabiting the planet Alphatron featured in Final Fantasy XIV.
An unknown time before the events of Final Fantasy XIV, the Omicrons were biological beings. Due to the frailty of their bodies, they were constantly attacked and eventually enslaved by the planet's other inhabitants. To counter this, the beings augmented their biological bodies with technological enhancements, and became able to turn the brain into a computer system and become 100% robotic lifeforms optimized for war.
Omicrons in their roboticised forms are tall and thin with a vague humanoid shape. They derive their names from the designations of celestial bodies. M-017 being the designation of the Omega Nebula, giving the name to the chassis Omicron M-017 later occupied.
Prior to Final Fantasy XIV
Millennia prior to the present day events on Etheirys, the Omicrons were a frail, biological species on the planet Alphatron. To resist other species' attempts to conquer them, they began technologically augmenting their physical bodies and eventually completely turned into robotic lifeforms. This let them obliterate all rival species and control their planet.
Some time after that, the planet's resources dwindled dangerously, leading to the final war between the Omicrons, a civil war with two factions: the regenerators that wished to try and save Alphatron and invaders that wished to invade other planets to obtain their resources. Part of the Invader's motivation was the Omicron's awareness that there were other sentient species in the universe and their fear of the possibility that stronger lifeforms would eventually discover and conquer them. To prevent this, this faction of Omicrons made it their purpose to continue to grow stronger and conquer all other planets with species stronger than them.
The invaders eventually won out and launched their campaign of conquest throughout the universe, with their first conquest being the planet Gordhona and its people, believing their machines of war to be the people's masters.
The Omicrons' last conquests was the Dragonstar, home to the Dragons, whom the Omicrons regarded as the strongest beings in existence. As the war raged, the star was nearly rendered inhospitable to life. Only Midgardsormr escaped his world's annihilation onto Etheirys, carrying with him the eggs of his offspring, but the Omicrons' greatest weapon, Omega followed him. Omega's pursuit of Midgardsormr left it too damaged and far out of range to communicate with the rest of the Omicrons, or even remember the exact location of Alphatron, thus leaving the machine stranded on Etheirys.
Following Dragonstar's conquest, the Omicrons' main command unit, Stigma-1, was unable to determine a future course of action for their people. The unit realized there were no more stronger species to conquer, and thus no further need to grow stronger. The unit fell into despair of having achieved its current purpose while being left with no path forward and no worthwhile reward to show for its pursuits. The unit disconnected from the main command unit and stopped issuing commands to the Omicrons. The Omicrons, as a species, were left without a purpose and would spend the rest of their days waiting for orders that would never come. At some point in time, the Meteia came into contact with the Omicron people, absorbing their emotions into their collective.
The only known Omicron left, Omega, eventually found its way to the planet of Etheirys, but it was too damaged to properly function. The Allagan Empire discovered the machine and restored it to working form. The Empire used it to capture the dragon Bahamut, one of Midgardsormr's offspring, and spur a technological revolution. Omega was left asleep beneath Carteneau Flats for centuries after the Empire's fall.
Omega was reawakened to defeat the newly summoned Shinryu and avert a calamity. The Omicron fought the primal to a stalemate, both combatants having knocked each other unconscious. Omega was forced to create a pocket dimension after Shinryu's destruction to continue its mission to grow stronger and reunite with the other Omicrons.
Omega continued its experiments and involved the Warrior of Light in some of them. After every experiment failed to give Omega the answers it was looking for, it accepted the impossibility of reuniting with its brethren and lived the rest of its time alongside one of its creations, a chocobo named Alpha.
At Ultima Thule, Meteion included a dynamis recreation of a decaying Omicron facility. Many of its inhabitants were units operating on standby mode, awaiting orders from a command unit. Said, command unit, designated Stigma-1, or "Sir", could not determine the best course of action, with the species having reached the pinnacle of its purpose only to discover there was no future left for them and believing the Omicrons had become so specialized in war to find a new purpose for life. G'raha Tia used his experiences in life to show M-017, Stigma-1's avatar, that it was possible to redefine oneself and recreate their purpose, giving some hope for the stranded Omicrons.
With hope rekindled in Ultima Thule following the defeat of the Endsinger, the Stigma-1 sent out a single command to the Omicrons from where it slumbered in a long dead world: "Live."
This had the unintentional effect of awakening Stigma-4, the command matrix in charge of the war aspects of Omicron life, which in turn discovered the planet Etheirys and determined it as a planet worth conquering. However, before preparations for war could properly begin, the Warrior of Light, with the aid of the Loporrit Jammingway and the Omicron N-7000, implanted the command unit with a simulation of a fight with the Warrior of Light in the unit's predictive models. This led to the command unit re-evaluating its predictions, concluding that the mission was all but 100% guaranteed to end in failure for the Omicrons. With this prediction, the command unit abandoned the goal of conquest and began reconfiguring the Omicrons' purpose for a diplomatic mission.
Behind the scenes
Omicron is the 15th letter of the Greek alphabet. The word literally means "little O" (o mikron) as opposed to "great O" (ō mega). In the system of Greek numerals, omicron has a value of 70.