If you're playing a magician in Camrish, you will frequently want to cast a spell.  There are several statistics which are relevant:

* Your Thread Weaving (TW) step: (WL + your TW rank)

* Your Spellcasting step (IQ + Spellcasting rank)

* Your skill with the particular spell (IQ + Magery + spell rank)

* Your PenetrationBonus (just the difference between your Willforce step and your IQ step: so WL-IQ if you don't have Willforce, and Willforce adds to it)

* The size of the matrix you're using.  For a MentalSpellMatrix, this is the rank of that particular [Spell Matrix] Talent. A PhysicalSpellMatrix will have a listed size. (If you're using Raw Magic, see below)

* The [circle] (minimum Magery required to cast), cost, casting time, duration, class (Regular, Information, Area, or Missile) and any other notes about your spell.  Note that many spells require particular gestures or rituals to cast; people who forget these will be smited.

The steps you need to take are:

1. Put the Spell into a Matrix: check that the size of the matrix is at least as great as the cost of the spell.  Then, either spend ten minutes meditating to reattune *all* your matrices, or try to quickly reattune one to this spell.  This requires a roll vs. (WL+Threadweaving-the circle of the spell).  If you fail, the matrix collapses.  If you succeed, that matrix is now said to be "attuned" to that spell.

2. Weave any necessary threads: this requires one action per thread woven (though the SpellMaster advantage makes it faster).  Each thread takes up (at least) one point of the matrix's size.  Record the margins of success for your threads --- it makes a difference for as many of them as I could think of a mechanic for.   Look at the [Known Threads for Spellcasting]

3. Concentrate/sing/dance for the requisite casting time.  It's expected that you're gesturing and speaking as you cast a spell.  If you aren't, you must have woven a thread (see [Known Threads for Spellcasting]) to "Silent" or "Not moving"

4. Cast the spell: make a roll vs. your character's skill with the spell (e.g. IQ+Magery+Fireball rank).  Take into account penalties from the concentration/ritual step above, as well as range penalties (1 per yard for most spells) and [skew] penalties(1 per point of skew).  Note the margin of success, because it's relevant for spell resistences.  Add in your PenetrationBonus if you have one (Willforce + WL-IQ)

5. Direct the spell's effect: make a Spellcasting roll to see how well you've cast the spell.  You may hear me ask for this as a "Finesse" roll or an "Illusion Art" roll.  This is your to-hit roll for Missile spells, so note the margin of success for the target to dodge against.

6. Maintain the spell: your matrix immediately skews --- usually by a number of points equal to the total size used.  There may be times when it only skews by one point (Safe areas), n^2 points, or 2^(n+1) points.  After the duration of the spell has run out, if it's still attached to a matrix it causes that much more skew, and continues (please try to smooth this as much as possible: no spell should ever be causing 6 points of skew an hour; instead it should be 1 point per ten minutes).

7. Let the spell drop: you can drop a spell by detaching it from its matrix.  To do this other than on a maintenance interval requires a TW roll.  The spell will collapse in a number of seconds equal to the margin of success on that roll.  If you fail, the matrix collapses and the spell collapses.  If you critically fail, the matrix collapses and the spell continues as raw magic.
(See [Casting with Raw Magic])