Primaris Psykers are super powerful Psykers in the service of the Imperial Guard. They are known as battle-psykers or psyker lords. They are often rare and equally as dangerous and are given special care and supervision by the Inquisition and the Adeptus Astra Telepathica.
Primaris Psykers are rare and extraordinary individuals who wield the raw, undiluted, concentrated and condensed energies of the Warp before unleashing it at the enemy. They are capable of hurling bolts of ether-energy at their opponents, burning the foes' synapses and searing their flesh from their bones. They are viewed with a mixture of awe and fear by the superstitious Guardsmen whom they serve alongside, and utterly abhorrent to some commanders. However, their ability to combat the magicks of aliens and heretics make them valuable assets. A Primaris Psyker is usually attached to a high-ranking Imperial Guard officer who can direct the psyker's powers as the situation necessitates.
Primaris Psykers often go to war in uniforms daubed with wards and sigils of power. They, like all psykers carry a psycho-reactive staff made of rare woods and precious metals, through which they can channel their psychic powers and transform it into a searing weapon capable of cutting through reinforced ceramite and ripping the life force from those it strikes. They can also tear a hole in your tanks and reduce boulders into molten slag.
Surprisingly for the Imperium, they actually took heed on several backups as a 'just in case' if something goes wrong. Due to the constant risks of daemonic possession, a Primaris Psyker's wargear includes several fail-safes. Complete micro-circuitry and neuro-active wiring are connected to the psychically attuned crystals embedded in the psyker's hood or collar, designed to bleed away excess Warp energy. These, coupled with cranial surgeries undergone by the psyker to implant neural inhibitors (which tend to blunt the psyker's innate power as well), and a lifetime of training, give the psyker a reasonable chance at avoiding powerful psychic enemies and resisting daemonic influences, and if all else fails a Commissar is always ready to *BLAM* a Primaris who is found wanting.