Psyker

Psykers are individuals with psychic abilities in the Warhammer 40,000 fictional universe. Psykers draw their powers from the Warp, and hence are often in danger of daemonic possession and insanity.

Psykers of Different Races
Most races in the Warhammer 40,000 universe employ some form of psykers to their use on the battlefield, some are inevitably more potent than others.

The Imperium of Man
The Imperium employs various 'psykers' throughout the Imperial Guard and Space Marine Chapters to effective use on the field of battle.

The Imperial Guard
Although psychic mutation is frowned upon within the Imperium, certain mutants are recruited into use by the Imperial Guard as 'Sanctioned Psykers'. These mutants may draw upon the power of the Warp, unleashing it upon their enemies. They are also called upon to advise high-ranking officers, with varying degrees of success. Their limited training and equipment leads to them being more easily preyed upon by the perils of the Warp than perhaps the much more powerful Librarians of the Space Marine Chapters. Each time they utilise their power, they put themselves at considerable risk and are prone to have their minds destroyed in the process. That aside, they are still a potent force when deployed and used properly.

On the battlefield, Sanctioned Psykers can advise an officer and guide their command, protect him from psychic attack, or fire bolts of lighting from their hands.

Space Marines
Psykers are employed by the Space Marines in the form of Librarians. These individuals are chosen from among the most powerful psykers. Librarians are responsible for maintaining the records of the Chapter they belong to, and can also use their talents to divide psychic mutants into those that are dangerous and those that can be utilised by the Imperium. Librarians, having much better equipment, willpower, protection and training, are much less prone to the perils of the Warp than other Imperial psykers.

On the battlefield, Librarians are fearsome opponents, able to unleash devastating psychic powers and augment their own physical prowess.

Eldar
Among all the races, the Eldar possess some of the most powerful psykers, using their ability to divine the future to shape their fate and also unleashing devastating powers on those that oppose them. Eldar Psykers come in the form of either Farseers or Warlocks, the former being the more powerful. Farseers will lead the Eldar warhost against the enemy and shape the course of battle with their powers. Warlocks are typically bodyguards and possess lesser, normally defensive powers.

The Ulthwé Craftworld is said to possess the most and the best Eldar Psykers, due to its proximity to the Eye of Terror, and they can divine much further into the future and with better clarity than that of other craftworlds.

Legions of Chaos
The forces of Chaos host a great many mutants among their number. Chaos psykers can perform various tasks such as summoning daemons and unleashing devastating powers upon the enemy. The Chaos God Tzeentch is devoted to sorcery; legions worshiping Tzeentch such as the Thousand Sons possess a large number of psykers that can aid in battle. Other legions such as the World Eaters denounce magic and psychic ability in favour of the wanton bloodshed of close combat. Chaos sorcerors can unleash potent powers and are fearsome individuals, but are often mutated beyond recognition.

Orks
Known as Wyrd Boyz, Ork pyskers differ from those of the other races in that they don't draw their power from the Warp, but instead from the latent psychic powers that all Orks have. The Wyrd Boyz then channel this Waaagh! energy to inflict damage upon their foes.