Awful Invokation Ov Tzeentch

Tzeentch is a Chaos deity also known as the Changer Of The Ways, Lord Of Fortune  And Intrigue, Master Of All Like Things Whether Petty Or Profound. In this sense, I would classify him as an Ouranian deity, so far as labels apply. While typically portrayed as a male humanoid with a distorted shape and features including two faced tentacles protruding from his head like horns, I believe  that form and/or gender would have no relevance for such an entity. In fact, I experienced feeling of gender flux during my invokations.
Worshippers of Tzeentch are portrayed as "going beyond simple Bacchic excess to such a loosening of moral and social restraints that they lose all consistency of personality and become cackling, drooling tear-strewn maniacs"- that applications of this form of unfettered consciousness in the undoing of 
fourth-circuit conditioning or ego-dissolution/shattering illusions will make themselves readily apparent.
Tzeentch can also help towards implementing workings for realization of buried/subconscious desires or exploring repressed/denied facets of consciousness. Tzeentch works quite well as an antidote to third-circuit "Pure Intellect" states, keeping the mind from getting in the way. The "sleep of reason" as it were. Especially nice for finding a synthesis for two formerly incompatible opposites. Tzeentch plays the Fool who overcomes the "rules" because he neither knows nor cares about them.
For entertainment purposes, one could call upon Tzeentch as a way of experiencing Chaos directly- pure, unpredictable, undirected and unrefined information- Factor X.
"His is the Wheel Of Fortune that spins and spins, carried by its own momentum, and stops...perhaps never."
Without further adieu, I bring you...

Thee Awful Invokation Ov Tzeentch
For starters, of course, of course, one must set up one's working area properly. Try to make the atmosphere as strange as possible- surrealist art (I used the Goose Game board from "Surrealist Games" as the center of my Circle), interesting musick (Glod, Psychick T.V.- the last half of "Al or Al" works nicely), multiple mismatched incenses burning at once, unfamiliar foods, silly (but not TOO silly!) costumes (the "Dada Almanac" has some nice inspirational material in it). Oddly-coloured lighting. Whatever works for you.
Next, Banish/center as you will- Zen it- no future or past, just the eternal NOW.
Open up your consciousness/charge up/induce gnosis. (Seething/shaking worked nicely for me).
Now here, I used a combination Chaosphere/Vortex to open up a point-doorway to the "Realm Ov Tzeentch" (whatever the freep that is) as the vortex whirled, I started spinning to match its frequency.
After you've become suitably zonked, proceed with the Invokation. I'd recommend writing one out as a framework and combining it with improv.
Here's one that I wrote:

"Ia Tzeentch!
Lord, we invoke thee
Changer Of The Ways
You who are inconsistent even in your inconsistency
Lord of the Butterfly Effect
Source of the Madness
Lord of the Perverse, the Devious, the Bizarre
Radiating the multicoloured fires of Kaos
Open the spiral doorway and allow us to bask in the raw derangement of your presence.
Ia! Ia! Ia TZEENTCH!
I am Tzeentch
I am fluid, malleable consciousness
I am the derangement that leads to Illumination
I am the whirling spiral power
I am pure, uncontrolled Mind
I am the force to which all thought must surrender
I am the God that shatters all illusions
I am both the madness of the moment and the scheming which directs history
I am the Impulse and the Idle Phantasy, Schemer's Plan and Plotter's Dream
I am the direction leading into...What???
Ia! Ia! Ia TZEENTCH!
(gradually collapse into raving incoherency)
Around this point, work towards opening up and absorbing Tzeentchian energy (pore-breathing worked for me), letting go and becoming one with Tzeentch. I also used hyperventilation and extended the Invokation with glossolalia.
I've applied Tzeentchian power towards Cut-Up Oracles, Automatic Drawing/Writing (regular and "Chaos Language"), the Surrealist Exquisite Corpse, Sex-Magick as well as the aforementioned uses. One interesting effect is what I call "Tzeentchian Fire"- weird, multi-coloured flame that appears in visualization as extruding from your/Tzeentch's body that one can sculpt into shapes and Servitors. Left alone, it tends to imitate the things around it. I once used it to create a body for Tzeentch to inhabit, turning an Invokation into an Evokation.
So far as rebanishing's concerned, it comes in handy but isn't entirely necessary. Sometimes he'll just up and go on his own (especially after sex-work- a good orgasm generally works quite nicely as payment). Of course, it does help to clear your head and ground yourself afterward. 
Side-effect include strange, multi-coloured visions (I saw a Mayan temple once), odd voices saying strange things (once, I heard "The Smurfs?! What are they, squeezin' 'em?"- I still haven't figured that one out yet). Generally, things get a bit weird for a time.

Quick Invokation:
Aksho Tzenneth Phaos,
(Tzeentch shall be called by fire,)
Ksy'lakash Dhaos Akhamshy'y Kaos Aksho'mi!
(The door is unlocked, Demons of Chaos I call the forth!)

Tzeentchian Flames...

Chaos Flames:
Octarine (TRUE) Flame: Powerful flames...
Black (DEATH) Flame: Shows enemy their death and brings it closer.
Blue (WEALTH) Flame: Material Gain...
Green (LOVE) Flame: Loving Eros's Arrow.
Yellow (EGO) Flame: Brings the mind together.
Purple (SEX) Flame: Sexual Eros's Arrow.
Orange (THINKING) Flame: Wisdom & Intelligence.
Red (WAR) Flame: Battle fire...

Other Flames:
White Flame: Healing...
Gold Flame: Energy And Speed.
Brown Flame: Purification And Perfection Of The Real World.
Silver Flame: Purification And Perfection Of The Spirit World.
Violet Flame: Transmutation.
Rainbow Flame: Brings peace and harmony to all.

Fiery Invocations:

Kaos Flames:

"By the power of Tzeentch within the fires of Kaos and the powers of the flaming eight-rayed star of Eris, I am evoking the (colour) Flame of (area of control). I am seeing this (colour) flame filling my wand/hand. I am seeing it before the silvered disk of the moon. I am seeing it filtering from the realm of Kaos. I am seeing it becoming concentrated, magnified and intensified until it...

Octarine: "is as one with the swirling disk of time, space, matter and shadow."
Black: "is as deep as the darkness of the eternal night dome of the sky."
Blue: "is as glittering as the gold is seeks to bring."
Green: "is as bright as the human light called love."
Yellow: "is as deep and radiant as the complexities of the human ego layers."
Purple: "is as vibrant and glowing as the post-coital sweat."
Orange: "is as deep and complex as human thought itself"
Red: "is as thick and clouded and the fog of the war which it seeks to bring forth."

Other Flames:

"By the power of Tzeentch within the fires of Kaos, I am evoking the (colour) Flame of (duties). I am seeing this (colour) flame filling my wand/hand. I am seeing it before the silvered disk of the moon. I am seeing it filtering from the realm of Kaos. I am seeing it becoming concentrated, magnified and intensified until it...

White: "glows like white gold."
Gold: "glows like its namesake, Fafnir's fall and Ottar's ransom."
Brown: "is as strong the earth and twice as deep."
Silver: "is as dream itself."
Violet: "is so varied that every possibility exists inside it."
Rainbow: "is shared of all the colours that exist and 13 more."

Servitor: Pink Horrors Ov Tzeentch:
Appearing as a nasty-looking cartoonish head set upon a pair of spindly reptilian legs with matching arms ending in large hands with conical fingers spewing Tzeentchian Fire, the Pink Horror has a mischievous, maniacal demeanor- especially useful if you want to stir up trouble somewhere. One advantage of note is that if the Pink Horror is "killed" by somebody, it splits into two identical Blue Horrors- much the same as their predecessor except for their colour and personality-the latter of which is generally the opposite- more dour  and miserable (which only goes to figure, if you think about it). I'd recommend including a subroutine so that they don't split if their creator kills them.

Servitor: Flamaz Ov Tzeentch:
Flamaz are amongst the most strange and disturbing of all servitors. Their lower portions resemble inverted mushrooms, whose stalks have been transformed into muscular bodies. Flexible arms which spit searing flame sprout from the Flamaz's unnatural body. Tzeentchian flames of all hues dribble constantly from orifices at the ends of the Flamaz's arms, roaring into life like living blowtorches as the Flamaz attacks. This is a fast servitor attacking with vicious Tzeentchian Fire magick. It's self-defense program is almost as destructive as its attacking programme and should only be used in the direst circumstances, never make one viral!

Servitor: Disc Ov Tzeentch:
Discs are unspeakable creatures of Shadow Space, shark-like predators that hunt the souls of astral projectors and pathworkers in the endless seas os the astral. They take the shape of flattened, plate-like creatures with vicious teeth and sharp spines. They have no limbs and move by hovering over the ground. It is possible to capture one and use it as a guide, mode of transport and even weapon upon the astral planes. Just keep it on a leash.

(Certain parts of this document where composed by someone else. See the main page on rituals to take your credit. Some of it has been stolen from Games Workshop, but that doesn't matter. The rest is mine or someone elses. Feel free to take, steal, chop or change as long as you remember to name me as part of the inspiration and also the previous author must be name-checked.)