The Nephilim are an insectoid race from the center of the galaxy.
While no definitive history of their existence exists among the various races of the galaxy, it is believed that the Nephilim are natives of an empire near the galactic core. The only race who knew of the Nephilim's existence were the Kilrathi, who had predicted their arrival in the known galaxy for centuries preceding their war on humanity. Thousands of years before, Sivar, the Kilrathi God of War, had appeared to the first Priestess of Kilrah and he set in motion a prophecy that would predict the doom that would rain down on the galaxy:
- "There shall come a time when one who has the heart of a Kilrathi, but is not Kilrathi born, shall rain cleansing fire down upon us. And Kn'thrak, a time of great darkness, shall embrace us
Death itself shall pour forth, obscuring the stars in a veil of darkness. Theirs is the claw that tears flesh from bone.
Theirs is the poisoned fang.
Their numbers shall rend the universe barren and crush the breath from our clans. We shall be bathed in our own blood and rotted flesh shall be our fare. With a deafening thunder shall the dark age begin."
- ― The Tome of Sivar
Around 2600, The Terran Confederation had sent Remote Deep Probe 12 towards the galactic core and reported "a warlike empire of almost unimagined strength" 10,000 lys away and expanding outwards, its only report before disappearing in 2629. The Kilrathi were also aware of them, and had make a choice: to confront them, leaving their outwards flank open to the Terrans, or create a buffer zone in the Terran direction before facing the inwards enemy. While Lord Vakka proposed to build strength instead of attacking the Terrans, the Emperor's circle advocated that the Confederation must be defeated as soon as possible before addressing the Darkness from the center of the galaxy.
During the year 2681, Kn'thrak made itself apparent to the inhabitants of the galaxy. During a routine research operation in the remnants of the Kilrah System, the TCS Devereaux, a research ship in the service of the Terran Confederation, encountered strange signals coming from an unknown source within the system. A few minutes later, an alien wormhole emerged and a massive warship entered the system. Several piloted TOBY Drones, the spacecraft deployed by the Devereaux to mine the Kilrathi asteroids, were destroyed as the ship plowed into their flight paths. The ship then opened up to reveal a massive plasma gun targeted at the Devereaux. The human crew sent a distress signal to the Terran Space Navy via a signal probe that was launched into human space seconds before the alien vessel fired upon the Devereaux, killing everybody on board.
Soon enough, dozens of mysterious warships entered the Kilrah System through the wormhole, setting the stages for an invasion of the galaxy.
Within the following weeks, several Kilrathi colonies, warships and space stations were destroyed by the Nephilim, as well as the majority of the Terran forces sent to investigate the attacks. Virtually no one survived these attacks, so both sides remained mystified as to what these attackers were and what they planned. However, that would soon change. The TCS Midway, a newly-commissioned Midway-Class Heavy Carrier, was in the middle of its shakedown cruise when it received a distress call from a Kilrathi cruiser in the H'rekkah System. By the time the TCS Midway arrived to save the Kilrathi, the vessel had already been destroyed. Lieutenant Colonel John Dekker led a contingent of marines on board the vessel to search for survivors, only to find that the entire crew had been individually dissected. Suddenly, unknown ships fired upon the Confed pilots, forcing both them and Dekker's forces to retreat. Realizing the severity of this threat, the Midway was tasked with eliminating these attackers.
The Terran-Nephilim War
The Midway trekked onward into the G'wriss System where their attackers began preying on human convoys. To make matters worse, these aliens were capturing ejected human pilots and were later discovered to be experimenting on them. Many helpless humans were dissected by the aliens behind the scenes.
- William R. Forstchen, Action Stations, Chapter 1
They were first introduced in Wing Commander: Prophecy and its online sequel, Wing Commander: Secret Ops.