In Year 338 of the Collapsar Zenith, tensions between the ruling hegemony of the Iridionian Dominacy and the more numerous members of the Energy Moiety reached a critical point. Civil war threatened, and to maintain their authority the aristocratic and authoritarian Force Moiety chose a method beloved by dictators everywhere: they started a foreign war.
They chose the Earth.
The iridionians' first move preliminary climatic warfare. This occurred in August 1969, while most of humanity were still celebrating the moon landings, unaware that alien powers mobilised in other solar systems. They sent stealthy vessels and agents to launch Medea-effect flares at key points around the planet while they marshalled their forces and stirred their populace with propaganda of Earth's strategic, material and cultural value as a jewel in the Dominacy's diadem. These flares produced a signal that precipitated an incredible wave of targeted natural disasters across the world, devastating Paris, Washington, Moscow, New Delhi, Beijing and Canberra. Though the world did not discover it until six years later, this was the first major assault by the Furies, who were roused and maddened by the flares' energy. The Primacy and local forces were hard pressed to deal with the catastrophes and aftermath on so many fronts, and the diversionary disasters served to keep them occupied while the iridionians prepared.
The world's first unambiguous clue about the impending attack was received on 24th November, 1969. Calvin Culverton, known as Captain Circuit (a low-level metahuman technical genius) noticed odd signals registering on the ARPANET (the prototypical model of the Internet), which had only been activated a few days earlier. The aliens were unaware that their technology broadcast on a pattern the primitive ARPANET could accidentally pick up, and just before the invasion began Culverton was able to decode the messages and send warning to the US government and the Primacy.
Iridionian warriors dropped from the sky around the world in ships or under their own power. They attacked with a two-pronged strategy: waves of weaker Spectral Caste troops dropped in wide dispersal across the countryside of many continents, create huge skirmishing battlefronts with the aim of blocking terrestrial movement and communications and tying up as many defenders as possible; while corps of elite veterans and Force Moiety officers attacked key cities and bases, forcing them to comply and gutting those that did not with energy blasts and advanced weapons. Few cities and superhumans managed to resist the invaders; in most cases, heroes were driven underground to wage a guerrilla war, and many were slain. The French superfencer Epeé perished dueling the Omphalous Caste champion Colonel Anotar atop the Arc d'Triomph, while on the streets of Kyoto the heroes Shokukumo (Eclipse Cloud) and Aoikanadzuchi (Blue Hammer) were captured by overwhelming Light Caste forces, and believed executed. Blue Hammer's sidekick, Aoikotori fled into the ruins, becoming a resistance leader. It was here that the hero known later as the Blue Swift earned his first scars. In Budapesht, an unknown young man was shot by an iridionian soldier, but his metahuman powers emerged just in time to save him. He became known as Lélek (Metal Spirit), and was soon seen harrying the aliens all across Eastern Europe.
The most notable city not to fall was Moscow: though it had suffered immense damage from an attack by the Furies, the precognitive heroine Zybille had foreseen the attack early enough to allow the Metahuman Shock Army to lay an ambush: dozens of buildings were booby-trapped, and airburst mortars set up all around. The incoming iridionians were cut to ribbons as they dropped, and two of the Soviets' strongest superhumans, Prizrachniyy (the Visionary) and Gora (the Mountain), led an MSA force to eradicate the survivors that fell onto an open field of rubble. Seeing that this was a global problem, the Soviet government offered sanctuary to leaders of nations that had been hardest hit. From an ultra-secure bunker called Kremlin Omega, deep beneath the city, the surviving heads of state tried to coordinate a counterattack - or at least a survival plan.
The Journeymen had been testing their new experimental starship, the Argus when the iridionians attacked. They were separated from Earth by the vast number of the iridionian flotilla, so they took refuge in the asteroid belt to plan how best to help. In the rock fields, they discovered the tunnel-cities of the cereans, last survivors of a planet that had occupied the orbit between Jupiter and Mars. The Journeymen galvanised the aliens and forged a great friendship with them, and waged a privateer's war against the enemy's interplanetary supply lines.
The Primacy was not involved in the government plans, but neither was it idle. Joe Clockwork discovered a plan to capture human nuclear silos, and use the warheads to eradicate the last bastions of resistance. The iridionians had neglected to bring their own weapons of mass destruction, considering their superpowers enough to add Earth to the Dominacy. The Primacy's Skyfortress had been damaged in the initial assault, forcing the heroes to travel on foot and by their own abilities. They scattered to defend numerous American, Russian and Chinese missile bases, occasionally reuniting when they faced too-heavy opposition. Sadly, they lost a few members, including the fire-wielder Emblazon and the royal-blooded martial artist Kingmaker.
At last, in a secret launch facility in Hawaii housing experimental antimatter warheads, they came face to face with the supreme commander of the iridionian forces, General Avon Starshadow. The immensely powerful Gravitic Caste warlord fought several members of the Primacy to a standstill, causing severe collateral damage to the island. The fight bought Professor Steele enough time to sabotage the weapons, rendering them useless. Starshadow withdrew, vowing vengeance, but a poorly chosen comment from Madam Rosary that he 'had the aura of someone she knew' set a sinister chain of events in motion.
Meanwhile, Captain Circuit had been monitoring the transmissions intercepted via ARPANET, and discovered that the aliens had come up with an alternate plan for mass destruction: they were moving their dreadnoughts into position just beyond the orbit of the moon, and preparing for bombardment. Firing at such range would be very inaccurate and taxing on the ships' power and ammunition supplies, so was not the first choice; but the frustrated iridonian commanders felt they desperately needed the fire support. Knowing that the heroes were otherwise occupied, he nervously resolved to deal with the threat himself. 'Borrowing' a prototype of the Argus from a NASA hanger, he launched himself into space at a speed he hoped was enough to avoid the iridionian point defense batteries. His ship plunged into the flag command, the Ever Ascending Battlestandard, and managed to infiltrate it in the confusion. Though hardly a trainer saboteur and barely a fighter, Captain Circuit managed to make his way to the central data core. Though vastly more sophisticated than the machines he was used to dealing with, his technical genius and computer affinity allowed him to create a makeshift interface. Overriding helm control, he ordered the Ever Ascending Battlestandard to crash into another ship on the iridionian fleet. The resulting havoc destroyed three ships and damaged most of the rest, breaking up their formation sufficiently and filling translunar space with so much debris that they were unable to mount an orbital offensive. Calvin Culverton was believed to have been killed in the blast.
The Primacy had kept the iridionians from acquiring planet-destroying weapons and Captain Circuit had removed their orbital assault capabilities, but their forces were still prevalent over much of the world. Two lucky breaks benefited the human resistance: Starshadow began taking a less serious interest in commanding his troops as his search for the person Rosary had alluded to intensified, and the Stellar Protectorate dispatched a contingent of Ascendant Guardians and Armatures to aid in Earth's defense. The cosmic-powered Guardians and their energy robots, though initially feared as a new wave of invaders, provided an incredible boost to morale and fighting capacity when they revealed their good intentions and power. Without their General's leadership, the iridionians fell back in growing disarray. Over several months of fighting, they were forced into a few heavily fortified redoubts. Tashkent, Santiago and Manchester still bear the scars of the prolonged and bloody sieges in their cratered landscapes and partial, alien-built barricades that remain.
Meanwhile, Starshadow completed his scouring of the monasteries and cathedrals of Europe. By torturing priests and looting records, he had found what he sought, and slaughtered his way to the Vatican. There, he met Darrow Sunhawk: his son, and a former ward of Madam Rosary and the church. Darrow had been thought lost in a space accident when he was an infant, but his escape pod had in fact made it to Earth. It crashed near a parish church in France, and the boy had been adopted by the local priest. Starshadow abducted his son and took him to the iridionian camp on the moon, planning to indoctrinate his son with his birthright. He believed that the two of them could regroup their forces and win over the Earthlings, and then return to Iridion in triumph and overthrow the other Castes to rule as monarchs.
The Primacy and a few allies, including Elyyor, the force commander of the Ascendant Guardians, travelled to the moon to stop Starshadow's plans, and by defeating him hopefully remove the will to fight from the holed-up iridionian forces. They evaded Starshadow's elite guard as they infiltrated the base, and arrived just as the General was activating the Coryx Convergence Stone, an iridionian artefact able to accelerate the development of their species' powers. As Darrow writhed under its effects, Avon Starshadow attacked the Primacy. This time, he had numbers and a home ground advantage, and the battle swiftly turned against the Primacy. At one point, Starshadow seized Joe Clockwork and literally hurled him through a wall at beyond lunar escape velocity, sending the android off into space. Another casualty was the Indian superhero Peacemaker, who was weakened by repeated attacks from iridionian soldiers, then finished off by a deadly self-defense mechanism which neutralised his attackers. Just as things look their grimmest, Darrow Sunhawk emerged from the Convergence Stone's radiance, and took his place next to his father. Starshadow gloated, promising destruction to mankind; but Sunhawk merely raised his hands, and all the iridionians save his father were blasted with incandescent multi-energy beams, knocking them all out. Starshadow discovered that what he had believed was true: his son was Unity Caste, a rare mutation capable of manipulating all forms of energy and the fundamental forces. And he was loyal to his adopted home.
Father and son fought as the Primacy looked on, but it was a very one sided duel. Sunhawk used his powers to disable Starshadow, and ordered him to leave the Sol system forever. Bitter and silently vowing vengeance, Starshadow gathered as many of his men as he could, and issued the order for the iridionians to leave the planet. He knew he could never go back to Iridion, because he was a failure and they now knew of his plans to usurp the Dominacy, so instead he took those soldiers loyal to him and retreated into deep space. The remaining iridionians loyal to the Dominacy quickly surrendered, though a few killed themselves or fought to the death.
The painful process of healing and rebuilding began. Darrow Sunhawk was offered a place in the Primacy, but declined, explaining that he needed to learn how to control his vast new powers. He was seen aiding the clean up and repair efforts for a while, but then vanished from sight.
The war had several consequences:
Earth won the eternal enmity of the Iridionian Dominacy and the rebellious Starshadow forces. Iridion has been dealing with civil unrest for the past few decades, so has not been able to mount a renewed offensive. It is known to support interstellar terrorist attacks against Earth, however.
Starshadow is reported to be lurking somewhere in a nearby region of space called the Hell Marches with his followers, acting as a pirate, mercenary, and bane of humanity. Recent rumours, however, indicate that he has been sighted near Ubyezhich. Clearly, he can't have been fighting Prizrachniyy (as a battle between those two would lay waste to continents). The concept of an alliance between these two is deeply chilling.
Darrow Sunhawk, wrestling with the incredible power within him, retreated to a secret Jesuit stronghold to meditate. This stronghold, called the Cathedral of Loneliness, is believed to be in an isolated part of Canada or an abandoned mission in the Nexus islands.
Elyyor left Earth to try and find Joe Clockwork, but lost the trail beyond the solar system. About a decade after the iridionian invasion, the Stellar Protectorate decided to appoint an Ascendant Guardian to Earth, realising that the young world, despite its limited space travel abilities, was in a uniquely dynamic position regarding extraterrestrial powers.
Clockwork eventually returned to Earth on a comet containing a miniaturised alien city and an ancient supercomputer, but that's another story.
There is a small iridionian population on Earth, consisting mainly of POWs kept in a few high security camps in concealed locations around the world. Their lifespan is considerably longer than that of the average human, so they will probably remain there for some time. A few have been re-educated, reformed and released, and now live relatively normal lives. More dangerous iridionians, such as the war criminals Rymak and Klaeon, are kept in Pacifica prison, which has the facilities to cope with their powers. There is, understandably, a considerable amount of prejudice against iridionians in the general population.