Set this up a while back, and now I'm filling in some things...
There are two obvious views of reality: that from physical space, and that from astral space.
All things are actually made of threads (is there anything other than threads that they're made out of?)
Is energy a separate thing from threads? It seems it might be...like matter and energy, they might be the same on some level, but for all intents and purposes they're distinct.
In order for a spell to be cast, there must be some sort of pattern which is then "instantiated" by infusing it with energy.
Intuitive mages shape the fabric of astral space around them into an appropriate shape, and then infuse it with mana or blood. Infusing the form with mana this way requires channeling mana through the self, a fatiguing process. This means it is possible for many mages to work together in the shaping portion of spellcasting, and that they (and possible others as well) can help contribute to powering the spell in ritual magics. However, it obviously requires the mages to be in contact with astral space in order to cast.
Threadweaving mages have two choices: they may cast with a matrix, or may cast 'raw.' Casting raw essentially uses the mage's knowledge of the spell pattern as the spell pattern itself, making the mage's own form (astral form?) the matrix.
From the point where a matrix exists, the steps of casting are fairly simple:
The Matrix must have a spell pattern in it.
The Matric must have a power source.
The Matrix must be triggered somehow.
(a matrix, being an object, also has DR and hitpoints as all objects do)
Lets look at a few specific examples of matricies:
The Caster as Matrix (raw casting)
The caster uses his own knowledge of the spell (contained within his pattern, presumably) as the spell pattern. Threads may be woven to modify.
The caster comes in contact with astral space, tapping the mana there as fuel. This usually consumes the mana bound in the mage's own pattern, which then is replaced from mana in the ambient astral space (which is poisoned by 'taint' in ED--fortunately, karma can be burned to purify astral space as it enters the mage's pattern, and karma rituals can be used to purge it even once it has entered)
OR the caster accesses kernels of true elements channeling their solidified mana through himself. This mana is pure (taint-free) though it may be aspected (better at fuelling certain tasks, because it matches the spell's form more closely), and due to the nature of elemental kernals, comes in multiples of 25 energy.
(OR the caster uses his internal store of karma to fuel the spell. I do not know if this is actually possible)
The caster triggers himelf (since he has access to his own pattern), and he casts.
Mental Matricies (using Matricies of Creative Thought)
The caster copies a pattern from memory into the spell matrix, using Threadweaving.
The spell matrix is connected to astral space, and the mana theirin can be used as fuel. In ED, the fact that astral space is poisoned still applies, but mental matricies are specifically made to purge themselves of taint (referred to as skew in the case of matricies), and can be aided in this by the mage specifically trying to purify the matrix (I have an image of a cloth full of water, which the mage can twist and squeeze, or perhaps a net full of little balls, which can be worked out of the weave). Again a matrix usually channels the mana bound up in it to power the spell, then refills from the the mana in ambient astral space.
The caster uses his arcane connection (a natural thread) to trigger the matrix, causing the spell to be cast.
If the spell matrix is damaged (I'm not sure what happens. This can cause it to lose its pattern? It's just fine until it falls appart (collapses) and then must be rebuilt from ambient astral space or the threads internal to the mage?)
Physical Matricies
The caster copies a pattern from memory into the spell matrix, using Threadweaving.
The spell matrix is connected to a power source. Usually, this is mana in the form of True Elements. Blood is another common fuel source (and seems relatively weak compaired to true elements, although this is sort of confusing--a typical human can give about 20 energy in blood without threat of death (although he will pass out soon), and could, in theory, give as much as 110 energy (this takes him to the "just dead" threshold)--meaning that a human has the equivalent energy of about 4 kernels, but may collapse before that much energy is extracted. A windling has about 2 kernels, an ork about 6, and a troll nearly 9, without any accounting for durability, whatever the heck that does). Karma batteries are the final notable fuel source, although we've been exposed to few of these.
Matricies that use True Elements must be refueled to continue working, or they will grind to a halt.
Matricies that use blood must likewise be refuelled. Many, however, are implanted in living creatures, which replenish their own blood supply (much more swiftly in the case of must adepts--what effect would this have?)
Matricies fuelled by karma batteries usually have the batteries easily accessable, so they may be recharged more easily.
Matricies which are fuelled by mana in ambient astral space will implode if there isn't ambient mana (taking, I'd expect, HP of systemic damage until they are destroyed), and in tainted space will become currepted by taint/skew, making casting through them much more difficult and possibly causing odd side effects in maintained spells. In theory, both conditions could be in effect--low-mana tainted astral space could result in a crumbling, degenerating physical matrix.
It might be possible to somehow "seal off" a physical matrix, such that it is not in contact with ambient (poisoned) astral space. In this case, it would dissolve from repeated casting rather than become tainted.
Finally, a matrix must be triggered to actually cast. For most matricies, an arcane connection between the matrix and the one wishing to cast the spell must be forged--this is almost always done through threadweaving, although anything that creates an arcane connection is probably effective. Some matricies may be specially built to trigger under certain circumstances (either using some form of detection, or whenever they have gathered enough energy to cast. Many general use adeptly items use this method, I suspect, triggering when karma is directed into them, or when they have drunk enough blood. Fire cannons seem to trigger when kernels of true elements are injected into them).
A grimore is a physical matrix, or rather a collection of physical matricies, like the mind of a mage.
A mage may trigger it once they have tied a thread to it. I can't think of any other good way to form a connection with a grimore, unless you've written it yourself.
A grimore, due to its compact nature, tends to be more shorthand about the spells than other matricies. This usually means that it have a pentalty to casting (i.e. a lower effective skill).
As for fuel...grimores don't use true elements. Grimores don't use blood. This means they must either channel astral space somehow, or use karma. If grimores channel astral space themselves, then they are slowly becoming tainted (and harder to use, unless there's some workaround there) the more they're used to book-cast (this could lead to ancient, tainted grimores, an interesting effect). If they're channeling astral space through the mage, then the mage is effectively raw-casting through a borrowed matrix. If they use karma, the adept caster is probably providing.
If diciplined spellcasters keep a grimore as their "spell memory" then they have the arcane connection of having written the book (thus they don't need to tie a separate thread to it for raw casting) and they channel astral space to fuel it--tying a thread to a grimore allows you to substitute it for your own grimore. Perhaps the penalty inherent in grimore casting comes from the fact that you're tring to use something as complicated as a grimore without it being a pattern item for you, making due with just weaving a thread.
When creating a physical matrix, only a few properties of the material matter:
One--can it hold the spell. I think this has more to do with how creatively you craft it than any other property of the material.
Two--what it it's physical resillience, as measured in HP and DR.
Three--if it is using its own mana as fuel and refilling form astral space, you need to know its 'mana density'--this, i think, is a trait related to size, and limits the cost of the spell being cast (otherwise, you're trying to draw more than is there, and it can't refill fast enough--it tears apart, as though in a low-mana zone).
Otherwise, what power source you're using and how that's recharged/how much you can channel through the item. It may be the case that trying to channel more mana through an item than it has will cause it to buckle, warp, and otherwise be destroyed as though it had too little mana.
Four--if the material has any resistance to taint, or ability to recover from taint, this should be noted. So far, I think only adepts and mental matricies have any such ability. Any other type of matric would have to be somehow scrubbed with karma to purify it should it become tainted, or pulled apart, the taint shaken out, and put back together (effectively rebuilt)
--zebediah
Cyberware disrupts a mage's physical pattern, creating "dark patches" of nonliving stuff in the mage's astral form, and beinding it somewhat out of shape, since there isn't really a correponding astral change to putting metal in one's body. It effectively "skews" the mages astral form as much as taint might. This gives penalties to magical actions, simulated (at this point) by a lower cap on the Magery advantage. I don't remember how taint affects intuitive magery, since my characters have been careful never to find out. --zebediah.
It seems like Name and inherent value (part of the Name?) should be relevant for spell matrices. If you're embroidering your robe with gold thread, that should be meaningful. That might just be mana density. Unworkedness might be a good substitute for value. --bts
Unworkedness seems to have a few noticable effects, so far--they turn the thoughts of horrors and some unworked things hold mana remarkably well (true elements and all that)--I'm not sure if that means working something decreases its mana capacity, or if it just works out the accumulated, crystalized mana that's built up in it. Living things also seems to hold mana quite well, in a very similar fassion--I think that's way unworked earth is solid in astral space. The claim from the SR books is, i think, that mother earth is "alive" and thus solid, but that seems less elegant.
Last--the fact that you're making a matrix out of gold may be important for aspecting mana--since everything is made out of threads, the threads that make up gold may be closer to what you want for the shape of some spell. Not an issue for mental matrix casting, since you're creating threads out of raw mana or something like that...or parhaps an issue, but since you're a nethermancer, weaving nethermantic theads out of yourself is relatively easy.--zebediah
Things that should also be thought about...Intuitive Mages apparently "look different" in astral space. I don't remember if adepts do, or if adept spellcasters appear distinct from adept nonspellcasters as a class. In addition, though mages have a distinct astral appearance (which can be masked, at least in theory) they only contact the astral when actually casting. So--what do matricies look like from astrarl space? They might appear "spellcasterly" or "adeptly" when inactive, and may or may not glow in astral space when they actually cast. More information required.--zebediah
The use of spell patterns opens a wierd and wonderful world of, well, wierdness.
Picture, if you will, a piece matrix--several distinct physcial object that, when arranged in the right way (and provided with a power source) can be triggered to cast a spell.
Now picture these "puzzle pieces" are all very artistic tattoos on different people's hands and feet. Each one might look like a matrix, but obviously be unable to cast anything interesting. However, the people do a dance...at the climax, if done exactly right, all the pieces are in the right place, and the matricies use the blood of the dancers to fuel a spell. Wham.
Bring that down a level...make one person have three tattoos. One on the inside of each eyelid, one along one of their limbs. They form an actual matrix only when both eyes are closed and the arm is in the right position, at which point either mana or blood can be channeled through to cast the "detect our netherworld home" spell. Subtle, no obvious matricies, and if the person knows the right pose (something odd, so they don't trigger it accidentally) they can use it as a guide.
You could even do neat things with tattoos and rings, or even some pattern inherent in an individual, to make a matrix that's totally personalized (or personalized to only orks, or only a certain bloodline, or elven intuitive mages...) If you were really, really good,
you could have a set of such pieces that can be assembled many ways, with more than one way being a legitimate spell. That would require being off the charts, probably, but it would be neat for ancient artifacts and whatnot.
But I'm getting wierd and woolly. More later.--zebediah