As for my story, it is a sequel to Descent 3. Immediately after the final movie events of Descent 3, you are called to one of the CED Dreadnaughts. From there, you are given a briefing concerning the alien virus and the origins thereof. Basically, you are told that both the CED and the PTMC have been trying to anolyze the virus and its origins. But while the CED merely wanted to learn about it to attack it, the PTMC wanted to use it against the world. You are updated about the alien planetoid featured in D3 Merc lvl 4. It was discovered by CED and then the PTMC sent in a Mercenary to destroy it if it was infected by the virus. Its inhabitants were a minor alien race (like our animals) that did not create the virus, but the station itself was infected. The CED believed the alien race that created the virus uses these planetoids to spread the infection. With their studies of the D3 planetoid and PTMC's studies of the D2 planetoid, the CED has discovered the origin of the race that created the virus. You are then given a Pyro-GX with a warp drive (like the one given to you in D2) to go to the alien system and spy on the alien race. When you warp to the alien system, you see a solar system that is 100's of years ahead of our solar system's time in respect to technology and colonization. All their planets are full of inhabitants and their space is full of space vehicles. You go to a moon belonging to a planet on the furthest side of their solar system. It is a military installation. While there, you hack into their computer system and download all the information surrounding the virus along with some basic data on the alien race, including their military statistics and some data on technology. But you are caught downloading the data and are imprisoned. You have to escape the prison, find your Pyro-GX which contains the information downloaded, and warp back to earth. That level will be done on foot, but other vehicles may be used. It is not a flying level. Anyway, when you find your Pyro-GX, you find scientists who just started examining it. They opened up your front compartment that contained the warp drive and were held in amazement (they did not have that technology since they never needed it). You kill the scientists, jump into your Pyro-GX, break out of the facility, and warp back to earth to report to CED headquarters. There, they download all the information and you're mission is over. Two years pass. You are awoken from your sleep from an emergency phone call from CED headquarters. "Material Defender, we have a serious situation, report to CED headquarters immediately!" You head off to CED headquarters. There, you are given a breifing that tells you first what the data you took from the alien military base had and the fact that there is an invasion force from that alien race at the edge of the solar system. Basically the planetoids from D2/D3 Merc were alien mining facilities. The aliens built a virus that would utilize the bee alien race so that their daily activies shifted to that of production of resources/energy. The virus was designed to spread to any machine/animal race without will to help the alien race gather resources. The virus spread to the solar system and started infecting PTMC mines to help gather more resources. Anyway, D1-3 stories happened and all that time the alien race was not aware of where their resources were going to come from, for it would have been nearly 2 years until the alien race recieved our solar system resources. Anyway, they had discovered earth from the Material Defender's Pyro-GX and they saw humans had a technology the aliens did not, warp technology. So they decided to invade and destroy the human race to remove their threat against alien resources and the alien race themselves. The aliens, after travelling for two years at high speed, had reached the solar system with a space force that could not be counted. Over the last two years, greater technology had been discovered, thanks to the alien data stolen, but the humans were still outnumbered. Nevertheless, the solar system had to be defended, so you and millions of other pilots are sent out to the solar system's outer rim to prevent the alien race from breaking through the asteroid belt. The battles continue to move closer and closer to the asteroid belt, on which the other side (near Mars) is gathered 100's of CED Dreadnaughts. You escape through the asteroid belt to these Dreadnaughts to make a large military stance (Mars has become a giant military base. Earth is full of civilians with only a few military bases). The aliens blast through the asteroid belt to get across and then a big battle occurs with big explosions. Yay! Anyway, to cut things short, the humans take many loses and are forced to fight going back to Earth. As you retreat back to Earth, you lose CED Dreadnaughts like crazy. Once the battle reaches Earth, epic cut scene. Children look up from the playground to see gunfire from the heavens. As they look, they see the sky become black as alien ships descend to Earth. The children stare for a few more seconds until their parents run to pick them up. The playground suddenly flares up into a massive nuclear explosion, for an alien space ship fired a warhead. The camera spins around the world to see alien space ships firing nuclear warheads everywhere. Cut scene ends. You recieve a message in your Pyro-GX about Earth being under attack by nuclear warheads, all military bases have been destroyed and the aliens are focusing their attack on heavily populated cities. In order to stop the nuclear holocaust, you have to activate a high tech Earth defense site at the South Pole. You descend to earth to the South Pole and activate the site. A massive EMP fires from the facility and all electronics are disabled for 1 minute. When electronics come back on, all high powered weapons, including alien nukes, are wrecked beyond repair. The battle descends to Earth. 50% of game then becomes these battles. Total levels should be around 50, about 1 hour per level. In the end, either humans win and Descent is over; or aliens win, humans escape, and Descent V is about taking Earth back. I haven't decided that yet.
EDIT: When battling around Mars, the battle occurs both around Mars in space and on Mars' surface. The name of this Descent IV is Descent IV: Invasion. Whether you are limited to Pyro-GX or can use other ships is for future debate as well as the ability of modifications to the ship's payload (weapons/armor/engine/abilities). Also, there could be no levels in this game, meaning everything occurs on one big level in order to add to the realism of the size of the game. Or, of course, you can split up the levels per massive setting changes. Descent is the game that the elites played in order to pwn all the noobs of today.