Critical Mass: The Xandar/Earth War
In the headquarters of the Fantastic Four, Reed Richards is concentrating on a highly sensitive piece of lab equipment. The leader of the FF suddenly hears a mechanical voice call his name and pleading for help. Richards turns to see a creation he thought long lost; HERBIE! When asked how he is still functioning, HERBIE explains that he had been rebuilt by the mutant named The Reanimator!
After he became fully functional again, HERBIE's link with the Living Computers of Xandar reactivated and the little robot received an urgent message from Xandar. HERBIE plays back the holographic message from Queen Adora who tells Dr. Richards that Earth is in danger! The Protector has gone insane and is planning to invade the planet!
On the planet Xandar, the Protector puts his plan to conquer Earth into motion. Since the devastating destruction of Xandar's homeworld by Zorr, the Protector has believed his race deserves a new planet. Not satisfied with the four-domed world they live on now, he has set his sights on Earth. Since the resurrection of Xandar, he has been secretly manipulating Queen Adora into amassing a space armada. Through an alliance with the Shi'ar Empire, the Xandarians now have access to Star Gates and Imperial starships. For their part, the Shi'ar have joined the alliance in order to gain access to Xandar's Living Computers as a potential weapon against the Kree Supreme Intelligence. Along with forming the alliance, Protector has been instrumental in the constant removal of Rich Rider's powers. Since his incredible power outburst on Epyrus 7, Rich Rider has been regarded as a dangerous element in the Protector's plan. Although Rider has been able to regain his powers, the Protector is determined to use it to his advantage.
Using the powers he gained from the Living Computers, the Protector sends Rich Rider to the future in order to prevent Nova's interference. While in the future, Rider encounters his old enemy, Megaman. By Megaman's side is his companion, the Entity. Recognizing Nova's costume, the Entity explains that the race she evolved from was the Xandarians not the native Earth population. As a result of the Xandar/Earth War to come, the Xandarians became the dominant race on Earth. Megaman realizes that if Nova can prevent the Xandar/Earth War, his fate will be changed and he won't be a captive of the Entity. Nova and Megaman battle their way to the black pool which is a portal back to their own time. As they are about to jump into the black pool, the Entity unleashes a fatal blast towards Nova. She also realizes that if Nova prevents the Xandar/Earth War, she will no longer exist. In a courageous act of self-sacrifice, Megaman knocks Nova into the pool and takes the full impact of the Entity's blast. He dies knowing he may live again if Nova is successful.
During this time, Reed Richards has gathered the Fantastic Four and they use Reed's starship to travel to Xandar. Arriving in Xandar orbit, the FF become embroiled in a massive space battle with the Shi'ar ships. After successfully fighting their way onto Xandar, the Fantastic Four find Adora. The Xandarian queen leads the heroes to the Protector in the hope they can stop his attack on Earth.
Back on Earth, Nova accesses a Star Gate to return to Xandar. Arriving on Xandar, he is quickly captured by the Protector and the mind-controlled Nova Corps. Regaining consciousness, Nova learns of the Protector's plan to conquer Earth. The Protector plans to create a being called Dark Nova by merging the entire Nova Corps into one being. After Dark Nova and the Shi'ar starships have weakened Earth's defenses, particularly Earth's super-heroes, Rider's powers will be added to Dark Nova's so he can eradicate the surface of the Earth.
Suddenly, Queen Adora and the Fantastic Four burst into the room and demand that the Protector release Nova immediately. Adora reveals that she has secretly known of the Protector's plan for some time and had been attempting to prevent the invasion of Earth. She even expanded the Nova Corps role from one of protecting only Xandar to policing the galaxy in order to find an uninhabited world for Xandar to colonize. Her hope was that the Protector would no longer need to invade Earth and abandon his plans. Left with no other choice, Adora confronts the Protector and is quickly disintegrated by her powerful foe.
The Protector battles the Fantastic Four and manages to defeat them soundly. He finishes his Dark Nova creation and the two depart for Earth. The Xandarian madman informs the Human Rocket that he will be brought to Earth when it is time.
As things begin to appear hopeless, Nova hears a voice calling to him. Rider is not sure if it's inside his helmet or his mind. The voice belongs to Rhomann Dey, Rider's predecessor. Dey explains he is communicating with Rider through the Living Computers of Xandar!
The Living Computers contain the memories and essence of all Xandarians upon their passing. The souls of all previous Centurion Nova-Primes can communicate with their successors but only after a certain level of expertise has been reached. Along with communicating, the current Centurion can access his predecessor's battle experiences and memories. Rider hasn't quite reached that level but the situation warranted the Centurions' intervention. The Centurions disagree with the Protector's plan and it's their will that prevents the Protector from directly eradicating the Earth. However, they don't have the numbers to prevent Protector from completing his plan. They had tried to communicate with Rider before, but without the proper skills, it resulted in wild power fluctuations. Reed Richards' dampening of Rider's powers has given him the stability to communicate with the Centurions.
With Dey's guidance, Rider is able to bust loose of his restraints. Nova rushes to the aid of the Fantastic Four. Regaining consciousness, Reed Richards tells the young hero that the FF will stay and try to stop the starships from reaching the Star Gates. The FF's leader explains that Nova must get to Earth and stop Dark Nova and the Protector. Nova starts to express his doubts about being able to stop them but receives strong words of encouragement from the FF's rock-skinned member, the Thing, who has worked with Nova before.
Outside the Protector's headquarters, Nova receives help from Tanak Valt, Rider's successor as Centurion Nova-Prime after the Xandar/Skrull War. Valt informs Nova that the other Champions of Xandar, including the Comet, were killed in Nebula's attack on Xandar. He also reveals that the Protector who fought with the Champions against Nebula was not the true Protector. After the Xandar/Skrull War, the original Protector left Xandar to explore space and gain knowledge. In order to protect Xandar, he left behind an energy duplicate with a fraction of the original's power. For the honor of the Champions and for the lives of the Nova Corps, Valt helps Nova escape to a Star Gate.
To Nova's amazement, the Star Gate refuses to allow him to return to Earth. The Protector has denied Nova access to his homeworld! The Centurions are at a loss on how Nova can return to Earth without the Star Gate or a Nova Prime Starship. However, Nova has a plan. His talk to the Thing reminds him of their battle against the Monitors. During that adventure, Nova was able to create a space/time warp by utilizing the electron path of an exploding star.
Nova has the Centurions locate a star that is about to go nova. The Protector's refusal to shut out complete access to the Star Gate has given Nova the opportunity he needs to reach Earth. Using the Star Gate, Nova appears in a distant star system just in time to see the star explode! With great courage and determination, Nova survives the space/time warp and finds himself in Earth orbit!
As he rushes towards his endangered planet, Nova uses the radio in his helmet to communicate with Vance Astro of the Avengers. The young hero explains to his former New Warriors' teammate that all of Avengers and the New Warriors are needed to help stop Dark Nova and the Protector. Vance tells Nova that the Avengers computers have detected the arrival of the renegade Xandarians and will do everything they can to stop them.
Back on Earth, Rider joins up with the Avengers and the New Warriors and begins battle with Dark Nova. While Dark Nova has the edge in power, Nova has access to the experiences of the Centurions and the battle seems to be too evenly matched. The Protector steps in and blasts Nova away effortlessly. As he sees his fellow heroes being defeated, Nova realizes they need an ally to fight the Protector. Nova turns to the only being he knows who has the necessary power and experience with the Living Computers; the Sphinx!
Rushing to the area of their first battle, Nova yells out for the Sphinx. Suddenly, the Sphinx's Pyramid of Power appears with the Sphinx asking Nova why he has disturbed him. Nova explains the situation and is able to convince his foe that it is mutually beneficial for them to fight the Protector.
The Sphinx tells him that the Ka Stone must be reformed in order to do battle with the Protector. Between the Sphinx's knowledge of the stone and the Centurion's science, the Ka Stone is quickly rebuilt. While it's being reformed, Nova learns the Ka Stone's origin.
Given information by the first Centurion Nova-Prime, Jopal Kelv, Nova discovers that the Ka Stone was originally built by the Xandarians!
Thousands of years ago, the Xandarians discovered a gravimetric energy source/dimension that contained immense power. They harnessed a fraction of this power and condensed it into a single crystal that they used as a planetary defense/energy source to protect and power the planet. However, the condensing of the power into a compact source eventually triggered sentience in the crystal.
This evil crystal attempted to destroy the planet but was temporarily disabled by the Xandarians after years of battle. The crystal was then expelled from the planet and the Andromeda Galaxy where it eventually became part of the legendary Lifestone Tree. After the tree's eventual destruction, the Ka Stone landed in ancient Egypt. The ancient Egyptians discovered the crystal and built a great pyramid to store it in. The crystal (now called the Ka Stone) was found years later by a Pharaoh's former wizard and became the Sphinx.
Years later, on Xandar, the planet has rebuilt itself and the Living Computers have since been created. The Living Computers decide to try using the gravimetric energy source/dimension again. Instead of condensing it into a non-organic crystal, the computers discover that organic beings' cells can contain the gravimetric matrix and, properly manipulated, would give the possessor great powers. However, to avoid the mistake made with the original crystal, the computers would only give a small portion to any one individual. Thus, the Nova Corps is formed.
Meanwhile, the legend of the original evil crystal had spread throughout the Andromeda Galaxy. After Galactus destroyed the Luphmoid race, Zorr went to Xandar to find the energy crystal in order to use it to restore his planet. When he found the crystal was expelled to Earth, he destroyed Xandar and headed to Earth.
Back in the present, the Sphinx leaves with the Ka Stone to find the Protector. In the meantime, the Protector and Dark Nova have been able to defeat the Earth's super-heroes and begins to proceed with the final stage of his invasion. The Sphinx attacks the Protector and Nova begins fighting Dark Nova.
As the endgame approaches, Dark Nova attempts to drain Nova's powers in order to finish his assignment. Swearing he will never lose his powers again, Nova taps into his own energy absorption powers while diving into the body of the gigantic Dark Nova! At the same time, the Centurions removed the power dampening inhibitors previously put in place by Reed Richards. With the encouragement of the Centurions and his own incredible willpower, Nova not only prevents the power drain but he begins to drain Dark Nova! The power drain causes Dark Nova to change back into the Nova Corps who fall to the ground unconscious.
Nova, with his increased power, turns towards the Protector. The Sphinx and Nova are able to blast the Protector with enough power to cause his energy form to disperse in a spectacular explosion. Nova faces the Sphinx. As the Avengers and New Warriors begin to revive, the Sphinx realizes he cannot win and Nova can barely contain the power he now holds. They mutually agree to end hostilities.
Nova flies into space and releases the power towards the Star Gate. The power blast goes through the Gate and finds its way back to the Living Computers of Xandar. With the threat of the Protector gone and the Queen dead, the Centurions inform Nova that they will govern Xandar. They also vow that Xandar will never threaten Earth again.
Back on Earth, the Avengers and the New Warriors look up to see a small starship come through the atmosphere. After the spacecraft lands, the Fantastic Four and Nova come out and Reed Richards explains that he used HERBIE's systems to override control of the Shi'ar starships and shut them down.
After explaining the events on Earth, the Avengers' leader, Captain America, turns to Nova. The star-spangled hero salutes the young hero's courage and determination. After shaking Cap's hand, Nova looks down at his own hand. In it, Nova finds an Avengers Identicard with the words 'NOVA - Honorary Avenger' on it. Stunned, the young hero looks up at his fellow heroes to see them all smiling and applauding. Nova quietly whispers "Blue Blazes" as a single tear goes down his cheek.