My post that talks about what possession is and the levels of deity assumption http://www.spellsofmagic.com/read_post.html?post=501555
First off why would someone want to horse a Deity/Spirit.
There are five main reasons (of course this is not all) why someone would horse a Spirit of whatever size.
1. Training Purpose - Sometimes things can't be taught to you through words, you need to be actually shown or watch over carefully.( This is how Raven got taught pathwalking with the help of Loki) As well sometimes the beings want to use a body to teach someone else.
2. Information Purpose - When a spirit-worker is working say with a client, they can hear the information they are getting and translate it, to the client .Some Gods would rather come in and talk face-to face with someone so the information does not get messed up and that way they can also personally answer the questions.
3. Public Devotional Purpose - This is a real valuable public service because for some people seeing someone horse a deity and then maybe getting the chance to talk to them face to face is a very important thing for them, as well as for the Gods themselves.
4. Errands for the Deity - Sometimes the Gods wish to do stuff in our world that requires a body, mostly this will be for ritual or one-on-one meetings with their dedicants. Though it can be anywhere from a simple conversation to something like a marriage to a mortal god-spouse.
5. Channeling Spirit-energy - This is more to do with shamanic work, where the person is being a channel for a spirit to come through and help aid a person who needs help. Most of the time this is only the energy of the spirit coming through which is referred to as "aspecting", but sometimes can lead to a full-on spirit possession.
Dangers of Horsing
Horsing can be a very dangerous thing and should not be taken lightly. When a God/Spirit full-on possess you, you have no control over what they do to your body. There is chances that they may do something which is illegal, they may hurt someone, or they may hurt your body. Tthey could very easily ingest things your allerigic too, or they can decide to drive a car and run a red light, which can lead to a accident. Most of the time they will respect your body enough to not do something like eat peanuts if your deathly allerigic to them but this is not a for sure. Sure you can sent ground rules for them but who is to say they won't break them. ( The Norse God Loki likes to break rules after all) Also its wise to have people around that understand the God/Spirit and know what they like and dislike, you don't want to offend them. I stated this in my other post at the beginning but I will say it again, they are huge, and even if they don't put all of themselves into a person, there is still a chance that its to much for our phyiscally bodies to hold, and that can cause some problems.
You can very easily become addicted to it. When a deity comes through its a amazing feeling (or so I have gathered from my studies) and that feeling can make you feel very important, plus you may like how their massive energy feels on your body,and you may want to get that feeling all the time, that is not something that is good or safe to want.
Being horsed by a deity can cause problems in your relationships because the gods will say whatever they want to and do whatever they want to and they don't care if it hurts peoples feelings. Even though its the god that has control of your body and is saying certain words, its still is done with "your" body and sometimes people have a hard time with remembering that even though your infront of them, its not you.
Another thing you need to keep in mind is you need to make sure that it is a god. A lot of things will be more then happy to take over your body if you let them, and that can be a problem for people who openly horse whatever comes their way. If you have a deity who you work with they can see what is what and look after you so you don't get a bottom-feeding spirit entering you. If you don't work with any deities it may not be wise for you to be horsing.
Horses Safety/Sanity /Consent
Safety
The word safe for possession does not really work with possession because no matter how much you can research, prepare, make a better bond with your God, there is never going to be a absolute safe possession.Having a God/Spirit take over you can put a lot of stress on your system emotionally and physically. The person who is wanting to horse should think to themselves are they in good enough condition for this. If you have been not getting a lot of sleep, or your just getting over a really bad cold/flu, or if your having problems emotionally, or if you have any serious health conditions that can get bugged by possession, these are things you need to think about before trying to be a horsed. Of course from what was said above this does not mean that it won't or can't be done, but it would probably be a good idea to talk to whoever wants to ride you about these things, so they can be careful of your physical/emotional issues.
You want to make sure that your in a safe place when doing a possession. The way the Gods see a " safe place" can be a different view on how we see a safe place. They are very capable of putting us into some situations that are not the best and even though they are able to get us out of it, who is to say they will. It is always best to have someone with you or what they call a prep/aftercare team (you usually see these during rituals) These are people who the horse trusts and these people will take care of the horse before, during and after the possession. Don't take a God who is rough with the body as bad though. Sometimes the god has a lesson in place for the horse by doing this or this is simply the way the god is, and that is why research about the gods is so important. Also if you have a patron deity and your horsing a different god, its good idea for your patron to set limits so that the other gods/spirits don't take it to far.
Sanity
When a God appears in the body, there is chance they won't act how you thought they would have and they can act in ways that make you very uncomfortable and in ways that you simple might not like altogether. It is even possible that they take your whole ritual as a joke ( trickster spirits are good for this, but more often then not there is hidden valuable information in this) When this happens you don't want to just think well that had no meaning to it and forget about it, because you did not like what happened or what was said. You must take all things into consideration.
Nobody is perfect and we all have our issues to deal with but you should always be aware of your mental health and be working on it to better yourself. With that being said, once a god is inside they can see all of what you got going on and they may not think twice about moving things around so that things may come up right after the ride is over that need to be dealt with now, because it's what they wanted. Also if your one of those people who are in love with attention then this is something you need to get over. When a God/Spirit is going to enter you, you need to remember its not about you, its about them and trying to turn that around can have some consequences, such as the god simple not coming in after all the work and preparation has been done for them. Also if your allowing someone else to take control of you, you need to have a good understand of where you are, where you begin and end. People with poor boundaries and who are highly sensitive can get hurt by possession. This can be anywhere from people who suffer from egodystonic psychological conditions to people who have trust issues.
Consent
Most of the Gods/Spirits are aware that times have changed and they don't have the same number of people honoring them and that the shine's that were build to them many many years ago are falling apart or don't exist anymore. The gods have lived on without people honoring them for millenniums now this is not to say that they won't bargain with the remain people who honor them, but this is also not say that they are desperate either. You still need to treat them with respect because if you don't they will ignore you or worse do something to you because of your disrespect. This lack of people may give you more flexability in a sense though, you have every right to set boundaries when asked to do something that is unacceptable under todays rules. You should be working at setting boundaries with the gods you work with, after all this is a relationship and it works on both ends.
Some people see the gods in two ways. The first one is that we should be blindly obedient towards the gods and do whatever they say, when they say it because they are all-knowing, and all-powerful. The second people tend to think they are the all mighty and call on the gods to do their bidding whenever they see fit. People like this are just ignorant, etc etc. And yes the gods are more wiser and stronger then we will ever be but that is not to say that you can't have a proper give and take relationship and can make alternative arrangements for things.
In most possessory traditations there is a lot of structure that goes into it to try and make it less nonconsensual and less random. Now this is not to say that a Gods will follow this, they can pretty much horse who they want, but its not like its crazy simple for them. It takes work on their part and why would you want to try and possess someone who is kicking and screaming no at you, that would just be a pain. (Think of it as dealing with a kid throwing a tantrum, that is frustrating and not very much fun)
Natural horses who are not able to stop possession can get some control over when and where their posssession takes places. The Spirits/Gods are pretty good with working at creating some form of agreement, as long as it still follows what they want. If your the person who has nonconsenual possession its best that you talk to someone who has experience and information in this area to help you find a "balance" in this. Remember you can't walk away from something like this because it will only stop when the gods choose for it to stop but trying to set up terms may make the job easier. If your lacking a strong ability to set boundaries that's going to make things hard. You need to be able to set boundaries or your just going to become a living-walking vessel, living your life around visitations of your Parton Deity/other Deities/Spirits. If your walking down this path you need to set up something for yourself because yes this can be awesome but it can hurt you too.
Sources:
http://www.northernshamanism.org/shamanic-techniques/spirit-possession/dangers-of-horsing.html
http://www.northernshamanism.org/shamanic-techniques/spirit-possession/the-path-of-the-horse-is-contraindicated-for.html
Drawing Down the Spirits: The traditions and techniques of spirit possession by Raven Kaldera and Kenaz Filan
For my next post I am planning on talking about Preparation,Aftercare and Community Safety in ritual settings.