Making Magic
Mages may cast either improvised magic or use rotes (magical maneuvers). Either way, the final skill is based on the lowest skill of any of the spheres involved in the effect modified by the following:

+2 per Quintessence spent (up to Avatar level)
+1 for extended casting time (double minimum)
-1 per Sphere involved after the first
-3 must be cast instantly (as an active defense)
-X casting without focus (if applicable)

Spell Results
Spells can only succeed if the desired effects are within range of the amount of success. Each point you succeed by in casting can be used to "buy" one of the following effects:
Damage Multipliers
Most spheres may be used to cause damage. The effectiveness of a sphere's ability to do damage is multiplied by a factor. All of these are cumulative (so a Entropy 4 which is x4 used in conjunction with Life 2 which is x3 will cause x12 multiplier effect):

Example: Tasmania wants to heal Christoff. She uses her Life-15 skill (sphere level 4), takes extra time (+1) and rolls an 11 which is success by 5. Christoff is at touch range (0) and weights 200 lbs (3) so she has 2 points to heal Christoff with. She heals 2d x3 (life multipler) in that casting.

Example 2: Tasmania wants to turn an opponent to stone (try finding a coincidence for that ;). She uses her Matter-14 skill since it's lower than her Life skill (sphere levels Life 4, Matter 4) and rolls a 10. That gives her 4 points to use, 1 of which will have to be range (luckily he's within 3 yards) and another 3 of which are for weight (up to 1000 lbs). Unfortunately she didn't roll well enough to have points to spend on duration, so the target will only be petrified for one turn (duration 0 point = 1 turn).

Example 3: Christoff wants to fry someone (Forces 2, skill 14). He takes an action and rolls an 11 ("I swing a lamp at them, which breaks the lightbulb and electricutes them"), giving him 4 points of success. They are at touch range (he's in melee with them), there's no duration (instant damage only), there's no weight (damage affects whatever target is hit and the intended target can defend since it's not cast directly on him), so all his points go toward causing 4d (x1 multiplier for Forces 2) of electrical damage.

Countermagic
If a mage is the target of an effect he may resist if he has at least one point in any of the spheres used in casting. This countermagic roll is made against his sphere skill (highest if he has more than one to resist with) and his successes directly reduce the number of successes the opposing mage receives.

Failure
If the spell fails either by a failed skill roll or by not having enough points of success to cause the desired effect, then the spell fails. Further attempts to cause the same effect will be vulgar if possible at all.