When they detonate they release fine dust particles which are heavily impregnated with negative psychic energy. This form of energy is extremely rare; in all of human space it can be obtained only as a by-product of the Emperor's metabolism. Using the material to create anti-psyker weapons is considered by many to be a great waste, and their issue is strictly controlled. Psyk-out weapons are useless against non-psychic targets. Against psychic creatures such as daemons and psykers, however, their effects are devastating.