Psionicsts, normally possessing terrific offensive capabilites, may find
themselves helpless against a foe who has some sort of inate, or magical
resistance to their mental attacks. Upon encountering such a foe, they are
not helpless however, this battle simply becomes a battle of minds. The
psionicist's mind attempts to overload and weaken the defenses of the
target's mind. A successful psychic purge, can lower the ability of the
target to defend himself from mental attacks for a short time, allowing
the psionicist to press the attack.