From the Introduction:
Over the ages Inquisitors without number have proven themselves able to harness the energies of the Immaterium, bending them to their will and shaping reality around their desires with the force of their indomitable minds. It is not uncommon for an Inquisitor to influence the mind of a lesser man, to open a door or portal with but a wish, even to hurl incandescent bolts of balefire at his foes. But even the most innocuous cantrip can open a pathway for possession, attracting daemons from the warp like sharks to a drowning man. The fate of those unshriven in the eyes of the Emperor is often far worse than any divised by man, as a psyker unsure of his talents can be torn inside out within the blink of an eye – his mortal soul the cost of his ignorance. Thus only the most capable and psychically gifted Inquisitors dare to use their powers on a regular basis, knowing full well that the slightest lapse in concentration could cost them, at the very least, their mind.
However, there are those in the galaxy in league with the very energies they seek to exploit, the Lords of Chaos; the Ruinous Powers themselves. To these foolish, corrupt or insane individuals, such dangerous knowledge comes quickly and easily. The most potent of these magi can conjure coruscating infernos with but a gesture, change their form with a word and cripple those who would harm them with a glance. But such eldritch knowledge comes at a terrible price...
A PDF supplement for Inquisitor covering rules for chaos psychic powers. This was originally published as an article in Fanatic but was later made available as a separate PDF for free download.