The optional Alternate Magic Rituals rule on M9 is used. Any kind of absolutely silent and motionless spell casting is not allowed however (at the very least, a magic user must either whisper an incantation or make some small gestures; also, no spell may be cast with foot movements alone). Though not addressed in the box on M9, hand gestures may be "toned down." These sorts of motions are subtle enough that onlookers must make an IQ+1 check (and possibly a vision roll) to realize a spell is being cast; this inflicts a -1 penalty to skill on the caster (and may be combined with one-handed casting for a total penalty of -3). The following table lists all possible ritual omissions and their associated penalty.

Ritual Omission
No foot movements
Subtle hand gestures
One-handed gestures
No hand gestures
Softly spoken incantation
No incantation

Disallowed Spells

Mages may learn, but not cast, any healing spell (such powers are only usable by clerics). Likewise, Gate spells may be learned, but not cast unless very specific, difficult-to-achieve, environmental conditions and/or other parameters are in place. There are a few exceptions, however: Slow Time, Accelerate Time, Suspend Time, and Time Out.

Armor and Spell Casting

As a lack of proper ritual can penalize a magic user, so can the presence of metal armor. The following table gives a list of penalties by location (remember, these are cumulative). Of course, the total penalty for wearing armor while casting spells cannot exceed -10.

Skill Penalty
Skull/Skull and Neck
Exception: Mail coif is only -1.
Exception: Face mask is only -2.
Torso/Torso and Groin
Penalty for front-only armor for this location is reduced by 1. Armor with a DR of 4 or less is only -3.
Penalty halved (round down) if only one arm is armored.
Penalty halved if only one leg is armored.
This penalty extends to leather (but not cloth) gloves.
No penalty.

So, as an example, suppose Perry the wizard was wearing a steel breastplate, heavy leather leggings, and plate on his left arm. His total penalty to spell skills would be -4 (-3 for the front-only breastplate, -3 (halved/rounded down to -1) for the plate arm, and no penalty for the heavy leather leggings since they're not metal).

Many enchanted armors impose less of a penalty or none at all. Some mundane but specially-made metal armors, like elven Silversilk, penalize the caster less than normal.

Grimoires and Time/Energy Reduction

M8 has a list of skill levels at which magic users enjoy a reduction in casting times and/or energy requirements (e.g. for a skill level of 15-19, energy costs are reduced by 1 point). These reductions are granted only if the caster studied his grimoire entry and notes for the spell in question 24 hours ago or less. The length in pages for an entry plus notes for any given spell is equal to its prerequisite count (M223-237) plus one. The cost (in dollars) of such an entry (if obtained through proper channels) is its prerequisite count multiplied by 75 (spells with no prerequisites cost $50; these amounts may be altered by the GM once play begins). The amount of time it takes to study a spell to cast it with eligibility for high-skill time/energy reduction is equal to (R + 1) × 5 minutes (where R = prerequisite count). Here's an example of all the above concepts:
Perry the wizard graduated from Arcana University a month ago. After a little adventuring, he hired a tutor to bring his skill in Fireball up to 15. He can now cast the spell for 1 energy less than normal, but he needs to study a spellbook. He purchases a 300-page blank book and pays the $300 license fee ($75 × 4 prerequisites) for the right to copy the Fireball entry from an accredited International Wizard's Guild archivist. This entry, plus his notes, takes up the first 5 pages in his spellbook (4 prerequisites + 1). That night, before bed, Perry studies Fireball so it will be less taxing to cast tomorrow. This takes 25 minutes ((4 prerequisites + 1) × 5 minutes). The next day, Perry blasts an ogre with a 2d Fireball and, thanks to his study-session the night before, only spends 1 fatigue point for the effect.