HUGE amounts of work still to be done, please come back later
Sources of info
The following Entries may be of use. A791002, Zims entry on the races of 40k (try to incorporate that in here somehow), A674868, a 40k Entry, A441325, another, A438743, and another, A231878, thats them folks.
Wbesites, http://www.games-workshop.com (home page) and http://www.games-workshop.com/community/gwnetwrok.htm (links to 40k pages of note)
The Imperium is formed by three main military fractions; the Space Marines, the Imperial Guard, and the Sisters of Battle.
The Space marines are superhumans, genetically engineered to be super-strong, super-fast, and super-smart. They receive the finest weapons of the Imperium. The Space Marines are also divided into fractions known as Chapters. Each Chapter has its own history and battle tactics.
There are a Thousand Chapters in the Imperium, each with a thousand marines, and it would be impossible to list them all. So, below are shown the most well known of the Chapters.
The Black Templar Chapter are one of the Second foundings of the Imperial Fists Chapter, and so still belive Rogal Dorn to be the Primarch. Rogal Dorn did not wish for his Legion to be split after the Horus Heresy so when they did the new Chapters had to prove that they were not heretics. The Black Templars never colonised a Home World and instead became the first crusade Chapter.
The Crusade, undertaken by High Marshal Sigismund, started 10,000 years ago soon after the Horus Heresy, and since the Chapter has never been fully assembled.
The Black templers are a fleet based Chapter using a large amount of the normal ship (Battle barge, Strike cruisers and whatnot), and many stranger ships such as forge ships and training vessels. Each Crusade will have at least one of each ship type, and will often be joined by parts of other Crusades. Each crusade is led by a Marshal, while te High Marshal is the head of the chapter and monitors the process of all the current crusades.
While the Chapter has no home world, it maintains Chapter Keeps on each world they conquer or reclaim for the Emperor. These Keeps take in Neophytes from the local population for training to become full battle brothers, and also act as points for a Crusade to be started.
The Black Templar tactics tends to wards short range fire fights and close combat assaults. This has made them important in many wars, especially Armageddon where they battled, to great success, on several Ork Hulks and in cleansing over run Hives.
The Ultramarine Chapter is the name sake of the largest of Space Marine legions. When the second founding split the legion, it broke into now less than 23 Chapters, and the Ultramarine Geneseed is the most common Geneseed with 1/3 of the Space Marines being in some part Ultramarine.
The Primarch Roboute Guilliman was one of the most influencial and powerful of the Primarches, and headed the Terran Lords after the Horus Heresy. The Chapter is really a prime example of how to build a Space Marine Chapter. It follows all the rule and guideline laid out in Codex Astartes, written mainly by Roboute Guilliman. The Codex lays out Chapter organisation, standard battle tactics and much more.
Due to the Ultramarines being the goodie goodie Space Marine Chapter, many dislike them. They have earned a large amount of nicknames, unfortunately, few of which can actually be put in a guide entry.
The Ultramarines do not come with a single tactic attached to them, unlike many other Chapters. The do however, have a very versitile force and can field any of the standard units with backup from all the normal vehicles.
The Imperial Guard are composed of countless men and vehicles, from the light infantry of Tanith to mighty Armoured Companies. Regiments are typically 2-3,000 men, and armies can be anything from a small garrison force to a mast crusade containing legions of infantry and tanks. The Imperial Guard is so vast that it would be impossible to name them all, as each world is required to provide at least one Imperial Guard regiment each year. This also makes providing a consistant uniform a logistical nightmare, so each regiment takes their uniform from their homeworld.
Below are the most well known of the Imperial Guard:
Sisters of Battle
The final faction is the female faction. These tough troops use flamethrowers and the such to eliminate. Need more info on these girls
The mysterious and ancient Eldar race was once the most powerful in the universe and far greater then the Imperium has ever been. Then came the Great Fall. Chaos destroyed Eldar race leaving the remainder to travel the galaxy in gigantic ships called Craftworlds. They are more technologically advanced than the rest of the races, except for the Tau. They are however, the most intuned with their psycic powers. Which has helped them encounter the truth. They fear death above all things as they believe when someone dies they become absorbed into a shadow world controled by Chaos. Thus they have developed spirit stones which trap a soul inside them once the wearer is killed. They are saved from Chaos but now must live the rest of there lives as power for the intense Eldar Technology.
The main warriors of the Eldar are known as Aspect Warriors. Each Aspect has it's own unique fighting style. The leaders of the Aspects are known as Exarchs. (But I personally call them Space Marine Killers) The most common of these warriors are the Dire Avengers. They are swift and their exarchs are armed with the dangerous Diresword. The Pheonix Lord (The one who created the aspect and is extremely powerful)for the Dire Avengers is Asurmen, the Hand of Asuryan. Below is a list of the Aspects and their abilities.
Warp Spiders- Warp Spiders use their warp jump generators to jump in and out of warp space unexpectedly springing traps on the enemy. Traps which usually result in a lot of deaths. With the Exarch's special abilities they can take full advantage of these assaults.
Striking Scorpions- The Striking scorpions are fierce and proud. The built in blasters in their helmets make them even more deadly close combat troops. Most men who tangle with one of these warriors won't live to tell about it. The Pheonix Lord of the Striking Scorpions is Karandras, the Shadow hunter. He is not the first exarch of the Striking Scorpions. Before him came Arhra, the Father of Scorpions, who turned to evil and is now known as the Fallen Pheonix. Rumors say he might be the leader of the Dark Eldar Incubus.
Howling Banshees- The only female aspect these warriors are not judged by the gender, but how easily they can tear an opponent to shreds. They use the Banshee Masks, which let out a terrifying shriek to give them an edge in combat. "Flutter like a butterfly, sting like a bee." The leader of this aspect os Jain Zar, the Storm of Silence (note that Jain Zar actually "means" Storm of Silence. this also goes for the rest of the Pheonix Lords).
Fire Dragons- Armed with deadly fusion guns and melta bombs the fire dragons live and breath "BLOW UP THAT STUPID TANK" or "KILL THOSE SPACE MARINES". Of course even the most powerful demons of chaos can be taken do by a squad of these hardened fighters. The Pheonix Lord of the Fire Dragons is Fuegan, the Burning Lance. Feugan is probably the most loyal of the Pheonix Lords.
Shining Spears- The only aspect that rides jetbikes, these are the essence of hit strong and fast....or get torn to pieces.
Swooping Hawks- The Swooping Hawks dive out of the sky and assault the enemy. With their awesome Exarch powers they can be practically unstoppable in close combat after they fire their weapons.(sort of) Their Pheonix Lord is Baharroth, the Cry of the Wind. Baharroth is believed to be the finest pupil of Asurmen.
Dark Reapers- The Dark Reapers represent the destroyer. They excel at blowing enemies up from long range. Their Pheonix Lord is Maugan Ra, the Harvester of Souls. When the Eye of Terror expanded it caught Maugan Ra's craftworld in it's grip and all was destroyed. The only survivor was himself.
Tyranids, as they are known after the first encounter on Tyran, are the most alien of all known to the Imperium of Man. They have been compared to a galactic locust swarm, remorselessly hungry and too numerous to stop. They are a nomadic, space-dwelling race which migrated from beyond the far Eastern fringe of the Imperium to devour all of us and the alien creatures we encounter.
Let me clear this now, the Tyranids have no grasp on technology, everything they are and use are biological, even their ballistic weapons are biological, but more on the weapons later. The Hive Mind, the single predatorial sense that bind all the creatures together is the driving force of the Tyranids. Some creatures are more in contact with the Hive Mind than others, these are called Synapse Creatures, almost like leaders they keep the lesser creatures in order.
When Tyranids Attack!
Hive fleets, the space-born monstrosoties of living tissue that the Tyranids have been known to contain hundreds of ships, containing millions upon millions of Tyranid creatures. They drift through space, only stopping to launch a full-scale assault on a planet, first dropping numerous spores to the planet, these either of mine variety or will hatch into more creatures. The main Tyranid force is then dropped and/or hatched, killing and devouring all who fight back. Next various grazers are dropped onto the planet to consume all other biomasses, as all this is happening the atmosphere is slowly drained away. Finally the creatures of the fleet are transported back to the ships and all that is left is a bare, atmosphereless rock.
The creatures are then reabsorbed by the Hive Ships, the biomass collected used to create more Tyranids and to evolve others in the giant reproductive vats of the Hive Ship. Tyranids have the ability to evolve very quickly, the genetic make-up of the creatures inside the vats changes every time, until they are perfect for fighting the defenders of planets and asymilating the biomass of planets.
Planets can have warning of an attack. Hive Ship's courses can be guessed and the ships themselves are so huge and numerous that they can be detected many thousands of light-years away.
Also the Tyranids have evolved scouting forces, these can send signals through the Hive Mind to encourage Hive Fleets to move to this planet as it has a great amount of biomass or variety of life-forms. These creatures come in two forms, Lictors and Genestealers, but more about them later.
Tyranid creatures come in many different forms and sizes, they are evolving so quickly and differently that almost every Tyranid Fleet encountered is slightly different from the last. The Imperium has recognised some varieties of creature that seem to be common to all Fleets, though they are sometimes very slightly different.
The Synapse Creatures
These are the creatures that filter the wishes of the Hive Mind to the lesser creatures. Synapse Creatures tend to be larger than the "normal" Tyranid creatures. These creatures are:-
Hive Tyrants - the biggest creatures in most invasion forces. These stand at about 20 foot tall.
Tyranid Warriors - Standing at about 12 foot tall, these are more numerous than the Hive Tyrants, but less dangerous. These make up the core of the synapse creatures.
The Gaunt Species
These make up the core of most forces and come in various forms:-
Termagants - Carrying a small bioweapon these creatures swarm in their hundreds and have been known to overwhelm defenders before the larger creatures even get close.
Hormagaunts - Carrying no bioweapons these Gaunts only have sything blades as arms and are extremely fast and agile, deadly when they get into close quarters.
Gargoyles - A winged version of the Termagant, these are normally the first wave of an attack after the spores.
Numerous other creatures of completely different shapes and sizes have also been evolved to sort out other tasks.
Zoanthropes - these, created from the biomass of the Eldar, have a massive psychic potential and make devastating psychic attacks, able to destroy the toughest of enemy tanks and positions.
Carnifex - These are massive creatures the size of a tank, and very able to take out enemy tanks with ease.
Raveners - Snake-like creatures that move even faster than the Hormagaunts, these are the scourge of the most heavily weaponed assault troops and enemy positions.
Lictors - These are about the same size of a Tyranid Warrior, and cameleonic scales that act as camoflage, letting the Lictor creep up on the rear of enemy positions. These are also used to scout out potential target planets.
Genestealers - First created in the genepools of a Hive Ship, these creatures have become an infestation on many Imperial planets. When the creature comes in contact with a human it plants a seed in the human's neck. This then transforms the human into a "carrier". The human is at this point being manipulated by the Hive Mind. The human then mates and the child will be half genestealer and half human, they may look completely alien, completely human or a mixture. They then mate and a small "cult" will grow. These cults hide out in the dark areas of planets where they are normally not discovered until it is too late, the cult is so big it has become a big threat. These cults are normally dealt with by the Adeptus Astartes (Space Marines.) If the cult is particularily big the Hive Mind would know of the abundance of life on that planet. Even after a cult is destroyed it is too late.
Ripper Swarms - These are the smallest creatures, about the size of a large dog these are the grazers that rip the planet bare of all biomass, they have also been spotted in many fighting forces, ripping defenders down with their sheer numbers.
Biovores - These are strange creatures, created from Space Ork biomass. They, unlike most other creatures avoid combat as they are a living artillary device. They launch Spore mines at their opponents and are usually deployed at the rear of the force.