Such as it is.
All "Magic" in Unholy Wars is powered from the same source within the caster (the source is something I'll get back to another time). Not everyone is capable of using magic and any players wishing to create a magic using character will have to purchase an advantage during character generation. This advantage allows you to develop magic powers and buy the skills later on in character generation or later on in a campaign. The advantage cannot be purchased after character generation.
As I said, all the different types of power are just different applications of the source within the caster and variations in style and application of magic are down to how the caster learns to use their power. As in real life there are a number of different types of magic, for example you have Voodoo, quabbalistic magic, blood sacrifices, rune magic and so on and so forth. Each type of magic has a fundamental principle attached to it, examples of these principles might be violence, healing, divination, pain, self improvement or sex.
These basic principles restrict the user in the scope of what they can do, for example it is incredibly hard to get a beneficial effect (healing say) from darker arts, not because it isn't possible but because over the centuries spent developing the spells, methods and theories attached to that type of magic no one ever thought about how to do something nice with the dark arts and as a result there are no spells for philanthropist dark magicians. Looking at it another way, it takes a particular type of person to be interested in the kind of nasty shit that is involved in black magic and that particular type of person is unlikely to be interested in helping others, less interested in spending an age developing spells to help others within the boundaries of black magic and pretty disinterested in learning them even they did exist.
In other words, the kind of person the character is will determine what kind of magic they are interested in, which will in turn determine what they can do, 99% of the time what the can do and what they want to do will match up perfectly.
There are exceptions of course, not everyone has full, unfettered access to information and teachers from all types of magic and some people will simply take what they can get. They may move on when they discover something more suited to their personality or the practice of magic may change their personality to suit their type of practice.
For example, Joe is a bit of a dick and wants power to get back at those who have wronged him. Joe gets into the quabbala(cabbala/kabbala/I forget) which involves a lot of preparation, careful research, patience and a clear head. It's not exactly what Joe wanted but it'll do for now. In this instance one of two things will happen. One possibility is that as Joe gets more and more into magical practice he finds out about other nastier arts that give immediate results for little effort and Joe may well end up taking his experience and applying those arts to his practices and end up conjuring demons and dark spirits instead of the more typical angelic beings of the quabbala. The other option is that the months of patience and research will have a calming, stabilising effect on Joe and it will act like a therapy, making his personality more suitable to the type of magic he practices and making him more powerful.
Either way, the more your personality suits the type of magic you are using the more powerful you will be.
Magical power is not just something you can hurl about the place in beams of light, again not because that isn't possible but because the methods of using and teaching are very rigidly defined and experimentation is difficult, time consuming and frequently dangerous, not to mention ethically unsound or seriously discouraged in many practices.
As a result each magical practice has a number of tightly defined spells (pretty much like D&D) based around three variables: Speed, power and cost.
Speed is the length of time required to cast the spell.
Power is the level of effect
Cost is how much it drains the caster financially, personally or physically.
At the moment I'm basing most spells on a points basis with 10 points being the norm. Someone creating a spell would determine how much each variable got. I'm still working on this so I'll get back to it.
Learning spells is also an area under development and I'll get back to that but for now I'll say that it is not a matter of just memorising the spell for later use - a would be caster must practice it before they get any good. On this basis spells will be treated almost exactly the same as skills with five ranks in each one but they require less experience to learn. Instead of spending the full amount of exp to learn the spell the user will improve their ability to cast it by.. well... casting it. There will also be a basic spell ranking level determined by the sum of all ranks in all the spells they know to give an indicator of how generally proficient they are at spell casting. The upshot of this is that they will get it wrong a damned sight more often than they get it right and this could cost them dearly if they take on powerful spells before they master the simple ones. On the other hand if they master a number of simple ones to learn the principles of spellcasting then they are at less risk from the bigger ones because they generally know what they're doing - they'll have scribed protective circles and runes dozens of times and have little chance of mucking it up for example.
Psychics are just another kind of spellcaster, albeit an undisciplined, dangerous powerful one. As I said, all these powers come from the same source so many of the same rules apply except psychics are far less restricted and can learn a very broad range of effects without worring too much about what kind of person they are and how it fits the principles of the powers they try to use. They can even develop new powers on the fly but it's dangerous. The downside is that they tend to burn out quickly and easily if they're not careful. Like spellcasters they should start small and work their way up but unlike spellcasters their only real restriction is themselves. They will not have a mentor who refuses to show them the good powers until they master the basics and they can just go for broke from day one.
Right, enough is enough, I have work to do.