Psyker

A psyker is a being who exibits the ability to use psychic powers. Most races have units that have these powers, whereas some despise them so far as to engineer warriors that activly seek out and destroy them. Some races are so dependent on psychic powers that they have based their entire civilisation around them. The powers come mostly from the warp, but in the case of the Orks, they draw from their collective Waaagh! power.

These powers may manifest themselves in many ways, from predicting enemy movements to projecting bolts of devistating psychic energy. Some can even aid the troops to more devistating attacks.

Imperial Guard

The Imperial Guard generally shun psychic beings. They have one unit that has psychic powers, the Sanctioned Psyker. They are trained at the Schola Progenium, where they recieve intense mental training and undergo surgery in an attempt to control these powers. They still suffer from Perils of the Warp, but any nearby Commissar will sort that problem without hesitation.

The powers are limited to minor psychic powers which mainly involve predicting what the enemy will do. They do have a ranged psychic blast, but this is quite weak and is likely to be of little practical battlefield use.

Space Marines

The Space Marines also shun those with psychic powers, but they too make use of one unit, the Librarian. He is similarly trained, but also benefits from advanced equipment, such as the psychic hood. These advantages coupled with his improved Space Marine physique make him a more useful unit than the Sanctioned Psyker.

The powers are slightly more powerful, but still nothing compared to some other races powers.

Chaos Space Marines

Chaos Space Marine armies are similar in design to Space Marines, using a Sorceror instead of a Libraian. They make use of beasts from the warp, randing from small creatures with sharp claws to one of four greater daemons of the Chaos gods. They are not afraid to use psychic powers, as if they succeed they will be blessed by their gods, and if they fail they may well be possessed by a chaos entity, increasing their power for killing.

Sometimes the gods intervene and allow the psychic troopers to use their special powers and spells. Some of these powers cause instant death, while some cause plague and misery, killing over a long span of time.

Eldar

The Eldar use of psychic powers is quite prolific. Their entire race is connected in one great link and some of their most powerful units have strong psychic powers.

These powers range from directing enemy movements to fighting battles on the mental plane. They can easily fry an enemy mind, saving on physical warfare. Ulthwe craftworld may also form together many of their most powerful psychic units into one group, making an expensive but devistating force.

Dark Eldar

The Dark Eldar are similar in nature to the eldar, but have given up the use of psychic powers. They do use psychic objects, but any psyker found on Commoragh are often treated as playthings, usually involving pain and suffering.

Orks

Orks certainly make use of psychic powers, but not generally drawn from the warp. A large mob of Orks tend to generate what has become known as a Waaagh! field. This field can then be used by Wyrdboyz. The powers drawn are often unstable, and too much of a build up will likely explode the orks head, devistating the area around him. A wyrdboy avoids combat, as most other fragile psykers, but they can throw green flames capable of melting many armours and killing the warrior inside.

The powers of the Wyrdboyz may be unstable and lead to many heads exploding, but the gain from these units are often seen by warbosses. They dont however tend to appear on the field of battle after tribes have advanced from the feral stage, instead the army relies upon more advanced technology, crude as it may be.

Tau

The Tau have not developed psychic abilities, possibly due to a chemical mixture in their brains that prevents access to the warp. Why they developed this is unknown, but it prevents the Tau empire from being so easily corrupted by the forces of Chaos. None of their units have psychic abilities and so lose any advantages of this on the field.

Necrons

The Necrons have long fought against psykers. This is due to their war with the Old Ones. They were the ultimate psykers, controlling and manipulating the warp before it became a place of evil and death. They used it freely to move about the galaxy and controlled their empire with it. When the Necrons attacked, they sent vast amounts of pain and death into the warp, and destroyed a good deal of the webways. As such, the Necrons do not employ psychic units. This may also be because the average Necron does not have the mental capacity to control the raging tides of the warp. The Pariah is a psychic abomination, making life for other psykers difficult by disrupting their link to the warp.

Tyranids

The Tyranid forces are highly interconnected and linked to each other using psychic powers. The Hive Tyrant acts as a node for the other forces on the ground. The Dominatrixes act as relays between the Norn-Queens and the other ground forces, helping to co-ordinate attacks from orbit.

They use the warp to communicate and travel through, spending a good deal of their time in the warp, travelling between planets to find sustinance. They dont tend to use their psychic powers offensivly, except by the Zoanthrope, whose psychic blasts are devistating to almost every unit in the game.