This spell was created by Korban the Grey, a wizard with a special hatred toward psionics and psionicists. After initial and tentative unsuccessful attempts to devise psionics- blocking spells, he decided that a different approach was needed -- if magic can not easily block psionics directly, then it can certainly facilitate the efforts of natural creatures with those properties.

The material component of this spell is a small piece of a psionicist or psionics-using creature (a drop of blood or bit of brain is preferred, but any once-living piece will do, i.e. not hair or fingernail clippings). In casting the spell, the wizard magically amplifies the aura of the component and projects it into the ethereal plane, in the hopes of attracting a number of cerebral parasites.

For each two levels of the caster, 1d4 parasites hear the call and arrive at the beginning of the following round. The wizard can localize the call somewhat, and so designate rough numbers to attack different opponents. For instance, a 7th level wizard can summon 3d4 parasites, and can direct all 3d4 to one psionic opponent, 2d4 to one and 1d4 to another, or 1d4 to each of three enemies, anywhere in the range of the spell. The caster can also summon them to a fixed location, such as inside a jar, for later use. The sole exception is when the creature from whom the material component was taken is present (and alive) within range. In this case, 1d6 parasites per two levels appear and all attack that creature.

Once they are summoned, the caster has no control over the parasites; they behave as described in the Complete Psionics Handbook. That is, each parasite on a psionicist will drain one additional PSP for each use of a psionic power. When a parasite has absorbed 6 PSPs, it reproduces by fission into two parasites. Parasites in the absence of an active psionic energy source each have a 1% cumulative chance per day of leaving (this applies both to jars and to psionicists who totally refrain from using their powers). Only a Cure Disease spell will otherwise remove them. They can be detected only by their effects or by certain spells and psionic sensing powers.