Anti-Psyker Weaponry
Several types of anti-psyker weaponry have been developed by the Imperium, Necrons and other races to counter psykers. For the Imperium, these include the Culexus Assassin and their psykout weapons, which have devastating effects on psykers. Weapons include psycannon, warp swords, and other psykers. Necrons have developed several Pylons that, once complete will completely separate the warp from the material universe, thus rendering psykers useless. On a smaller scale there are the Pariahs, Necrons made from humans with the pariah gene - this makes them, like the Culexus assassins, soulless, and severely debilitating to nearby psykers.
The Greek Alphabet system of measuring psyker potential also applies to measuring anti-psykers. The lowest recorded example so far is an Omega Minus (the polar opposite of an Alpha Plus).
Untouchables are similar to Pariahs, but are widely assumed to have less of a blunting effect (although an accurate comparison has never been made). Untouchables cancel out psychic power cast near them or around them. Some even have the ability to consciously focus their power. It is also possible for an Untouchables power to be overwhelmed by a sufficiently strong psychic force. Alizabeth Bequin, an associate of Inquisitor Eisenhorn, was psychically overwhelmed by the warp sentience of an ancient Titan she was attempting to disable. Wystan Frauka, an untouchable in the service of Inquisitor Ravenor, was also made "touchable" due to unusual psychic activity.
Lastly, the Dark Eldar, while not having any known psykers among their ranks, have developed weapons designed for psyker destruction. One of the most gruesome (and rare) is the Crucible of Malediction, a nightmarish device which contains the essence of a slain psyker tortured into insanity. When the Dark Eldar use this weapon, the psykers tormented soul is released and its power has the potential to consume any psyker on the battlefield.
Read more about this topic: Psyker