Magic - Variable Fatigue

Fatigue cost is reduced by 1 for every N points by which the skill roll is made.
N is based on the local mana level (see table to the right).
Mana Level fatigue
reduction
per
Recover Energy
skill level
region
-14 15-19 20+
no ~ 10m 10m 10m (na)
low 5 10m 10m 5m ...
normal 4 10m 5m 2m most of Eire
high 3 1m 12s 2s Ley lines
very high 2 1s 5/s 10/s nodes
Modifiers
Advantages
+1 Voice advantage. You can only take this bonus if you are incanting above a whisper: a normal voice or shouting.
+(1/8) DX or Dance at 14+. You can only take this bonus if you are using normal or exaggerated gestures.
Extra Fatigue Cost
+1 to allow no cost reduction(see above for cost reduction rules
+1 per doubling of cost thereafter (minimum of 1 if base cost is less than 1)
Other
-1 Each spell "on" (note, spells cast with items or Scrolls do not count as "on".) (pM10)
-3 Also concentrating on another spell that you are maintaining (pM10).
+ (1/8 skill) Performance/Ritual (Ceremonial Magic only, i.e.10x base casting time)
+1 if an appropriate focus is expended as part of casting the spell.
(permanent foci, which are not expended when used, exist, but are classified as magic items which add to skill for a certain spell or college)
choose one from each category
Casting Time
+1 For each doubling of the casting time. max: +4 for non-cermonial magic, +6 for ceremonial magic
+0 use base time (normal/default)
-3 per halving Reduced casting time (-3 per second for missile spells that require buildup)
Gestures
+1 Huge, exaggerated movements and dances *
+0 moderate gestures with both hands, some minimal footwork (normal/default)
-2 No foot movements (e.g. sitting)
-2 Only one hand to gesture
-4 No hand gestures
Incantation
+1Shouting
+0firmly spoken voice (normal/default)
-2Soft speech
-4No speech

* Shouting and Exaggerated Movements: Huge exaggerated movements costs fatigue when performed for a long time. Assume the fatigue cost is the same as that incurred from battle. If you are doing them during battle, the fatigue cost is covered from the battle. but if you're a cleric jumping around and waving your are about during ceremonial magic, this may take a long time. For the first minute, incur fatigue from combat fatigue table (pB134). and roll vs HT every full minute thereafter. A failed roll incurs another block of fatigue (from the same table). If you are also shouting, the HT roll is at -3.

Resisted Spells
Things are more complicated for resisted spells. Before you cast choose the skill level you are casting at; call it your adjSkillLevel. The margin you make your adjSkillLevel by is what the target will have to make his resistance roll by. If you want to save energy, then select an appropriate adjSkillLevel.
For example, Boris has a Sleep spell a skill 18. He is in a normal mana zone. So to save 1pt of energy, he will cast at adjSkillLevel 14. He rolls a 12. he succeeds and save one energy pt. His target, Mask, must make her Will roll by 2.
Note: If the target is sapient (a person rather than a spell or object), then the adjSkillLevel is capped at 16.
References: