One of the few modern magical writers who does look at incubi and succubi (or, succubi and succuboys), is William Burroughs:
...an incubus or succubus can be harmless, or it can be destructive. Like any sexual situation, the danger depends on how you handle it. All sex is potentially dangerous .... Our sexual feelings make us vunerable. How many people have been ruined by a sexual partner? Sex does provide a point of invasion and the succubi and incubi simply makes us intensely aware of this.
--from, A Report from the Bunker (V. Bockris.)
In the novel, The Place of Dead Roads, protagonist Kim Carsons enjoys several encounters with sex-demons:
He knew that the horror of these Demon Lovers was a gloomy Christian thing. In Japan there are phantom lovers known as fox maidens, and the man who can get his hands on a fox maiden is considered lucky. He felt sure that there were fox boys as well. Such creatures could assume the form of either sex.
According to Burroughs, peoples attitudes towards these beings may change, but such visitations are probably more frequent than most people suppose. He classes them as a type of familiar (they certainly are!) and notes that, like animal or elemental familiars, they are dependent on a relationship with a human host for their own development. Similar ideas can be found in the Kaula school of Tantrika, where there are rites for contacting such beings. The general approach is that you fuck them and they do you a favour in return. Burroughs speculates on the possibilities of increased frequency of contact between humans and sex-demons:
Sex is physics. If anyone could push a button an receive an incubus or succubus, I believe that most people would prefer a phantom partner than the all-too dreary real thing.
--From The Report from the Bunker.
Playing with such entities generally falls into the class of magical technique known as Evocation, and a form of Gnosis which is often the most effective is the so-called Liminal state, when one is half-asleep, half-awake. The body is completely relaxed, either from a relaxation exercise, or physical exhaustion; yet the mind is clear, and you simply allow images and sounds to arise before you. If you can learn to enter and prolong this state, then it is very useful for scrying, dream control or virtual (astral) explorations.
Erotic Evocation
To prepare for the Evocation of a Demon Lover, seek to inflame yourself through all possible modes of sensory stimulation - books, films, pornographic material, the diffusion of perfumes that have erotic association, body massage, masturbation without orgasm - any technique which serves to heighten your sexual arousal globally - that is, without being directed to any particular individual (real or imaginary).
The Evocatory scenario is a progression of intense sessions which
may begin as follows:
Dream Yoga
Once you have evoked your demon lover, you can choose to interact with it through dreams. One of the easiest techniques of Dream Control is to use a sigil. Since Im sure most people are familiar with the basics of Sigil Magick, I will merely draw your attention to the point that a sigil need not be either a glyph or mantra, but can also take the form of a scent, or sequence of images. You can use earlier practice in the Liminal Gnosis to launch a sigil to meet your Demon Lover in your dreams. You could even try and key the appearance of the entity to the triggering of a Lucid Dream.
Liminal Gnosis
If your earlier practice has been successful, you will already have some experience of the Liminal Gnosis. Sexual Arousal is but one of the entry-routes into this state, and you might try and find other routes. Interaction with the Demon-Lover can be made in this state, and you might find here that you get dreams which follow-through the encounter.
Mirror-Magick
The Liminal Gnosis can be enhanced by the use of a mirror. The use of reflective surfaces for interacting with entities has a long and venerable history, ranging from shamanic practices among the Moari, Pawnee and Nkomis of Africa, to the explorations of Dr. John Dee. Demon-Lovers may be summoned into a mirror, where they may be cross-examined. A cautionary note here is that Dr. Dee made the claim that from time to time, one of the spirits he contacted - a young girl called Midimi - would emerge from his scrying crystal and cavort about his study This could have interesting possibilities when working with a Demon Lover!
Whichever states you choose to explore, the next consideration is of course, what you are going to do. Well, the very act of experimenting with this approach should in itself be instructive, and at the very least, enjoyable. However, the following applications for Demon Lover work include:
Enchantment
Here, you are basically forming a Pact with the entity - using it as you would use any other kind of Sorcery Servitor - you fuck it and it carries out its assigned task (which is not necessarily confined to the sphere of sexuality). One technique is to seed the entity with a sigil, which will gestate within the body of the entity, in a similar manner to a wishing box.
Illumination
According to Austin Osman Spare, desires are spirits that wish to incarnate. You can deploy a Demon Lover to assist you with the formulation of an Alphabet of Desire, wherein each sacred letter can become a sex-demon in itself, to be used in acts of self-exploration and self-modification. Your Demon Lover can assist you in recognizing, binding, and integrating the hidden demons of your psyche which relate to sexuality and other primal drives.
Divination
Divinatory applications include dream-oracles, or flash-gnoses which may extend into the waking state. You may find, for example, that, following a request for a dream-oracle, your demon lover only gives you half the key, as it were. The other half is waiting in the waking world - some incident that sparks a moment of gnosis in which you realise the link between thought/emotion and some physical object or situation. Oracles are rarely straight-forwards.
Invocation
Traditional magical theory (such as it is) tends to frown on invoking entities such as Demon Lovers, as they are not considered to have enough of a developed persona to make it worthwhile. However, long-term magical use of such an entity does tend to build up the appearance of an independent persona, particularly if you make careful note of any quirks, personality traits, or mannersims that the entity seems to be displaying. I see no reason why, at some stage, you shouldnt try invocatory work with a Demon Lover. It could be instructive, if only for shifting latent sexual selves into the directors chair of the Ego.
Another problem relating to this work is also fairly obvious - that the Demon Lover becomes a substitute for a physical partner. As with any relationship between human and entity (be it demon or deity), it is useful to assume its independent existence - if only during the interaction. However, I have seen warnings in a variety of magical grade papers that hint of the dire consequences of giving these entities the same regard that you would a human lover. By the same token, conjuring a Demon Lover for the precise reason that you lack a human lover is tantamount to inviting obsession, with all the attendant problems. As success with this technique requires an appreciation of your own sensuality, bodily awareness, sexual feelings and orgasmic response, it should not be attempted by the overly frustrated, or the sexually inept or inexperienced.
This practice should also lead to a wider appreciation of your sexual being and possible range of sexual identities. If you have sealed disturbing elements of your sexuality behind blocks, then you might well find that this practice leads you into a situation where you have to confront these experiences. This may not be pleasant, but can be, if you allow it, instructive, and possibly healing.
If, for whatever reason, you do find that working with a Demon Lover brings up problems that you find difficult to handle, then there are basically three strategies which can be brought up. The first is to perform a thorough Banishing of the area you are using for this practice (i.e. bedroom). Secondly, you can evoke the entity and confine it into a spirit trap such as a triangle, bottle, or crystal, and ritually re-bind it to your will. Thirdly, there is the option of reabsorption, which can be performed as a ritual or within the Liminal Gnosis. The simplest approach here is to take back the entities name, destroy any material base, visualise the emotions/sensations/abilities you may have bestowed upon it as withdrawing back into your body and finally (and this can be difficult) denying it any sexual response or erotic association. Then, go and have a cold shower.