Traditional invocation is a technique magicians use to connect with entities. Invocation involves allowing the entity to access your consciousness and take partial or full control of your body. Invocation is done for a variety of reasons, as follows: Information: Invoking an entity can give a person access to the entity's knowledge, though usually the entity will want something in return. Since invocation is the easiest way to pass information along, what the entity usually wants is the opportunity to enjoy some time in the person's body, having experiences it might not normally have. The magician will share consciousness with the entity, allowing it a taste ofh is/her experiences. It will provide the information in return, so that the magician has access to it when needed. This type of invocation could be considered a form of divination, though usually it's for very specific information the magician wants.
Possession: Sometimes an entity will be invoked in order to give it possession of the invoker's body. For example, in voudon, the invoker will allow the loa to fully take over his/her body. This type of possession isn't limited to just voudoun, but you are less likely to encounter in other traditions. With this type of invocation, it is very important that the magician has other people on hand, both to keep his/her body safe, and to keep an eye on what the entity is doing, while also recording any information it offers. When the person is possessed s/he will move differently than normal, may talk in a different language, and otherwise will act like the entity. The entity will use the possession to express itself, not just in language, but in movement, and in whatever other ways it can, in order to convey its message to other people.
Healing: An entity can be invoked to help in a healing ritual. The magician will invoke such an entity when s/he wants to heal someone and wants to draw on resources the entity can offer to help with the healing. The benefit of invoking an entity is that it can help guide you as you're doing your healing work on the person. You can also invoke an entity when you want to ask it to heal you. This can be useful, because the entity is drawing on its own energy, as opposed to drawing on the impaired resources of the body.
Worship: In a religious context, an entity is invoked as a way to worship it. The person who invokes it doesn't allow it full possession, but will channel it, so that the worshippers can interact with the entity. The ritual that's performed to invoke the entity is part of the worship process.
I mentioned traditional invocation, which implies that there is non-traditional invocation, and in fact there is. I developed non-traditional techniques, which I've discussed in full in Multi-Media Magic, when I realized that invocation is a two way street. In other words, if I can invoke an entity into me, it stands to reason that I can also invoke myself into the entity. Pathworking, which is a type of meditation, where a person creates a virtual reality, can actually be used for that purpose if you're working with an entity. Invocation works on a principle of identification. In order to successfully invoke an entity, the magician needs to identify with the entity, and through that identification provide a pathway that it can use to access the body, mind, and spirit of the magician. But this same pathway and identification can also be used to invoke yourself into the entity. It's a matter of being able to understand it enough to access its consciousness. I've found this type of invocation most useful for obtaining information from the entity, but it can also be useful in a situation where you want to do an exchange of essence with the entity. By being able to access the entity in its native environment, you can get a better handle on the essence it provides you, in return for what you give to it.
You can also invoke yourself into a person. Since invocation is based on connection, if you can connect with the person, you can invoke yourself into him/her. I've invoked myself into people to help them unblock or heal themselves. I've also this practice as a way of aligning with other people when we do long distance rituals. This kind of invocation should only be done with the permission of the person you are invoking yourself into. It's important to remember that you will be getting access to that person's emotions, memories, etc., but that person will also be getting access to you and could just as easily invoke him/herself into you. I think it's ideal to use this kind of working to help someone work through an issue or to synchronize people before doing a major magical working.
Am I missing anything? Would you add anything else about invocation?