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:
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.
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.