Magic

Basicly magic is handled like any other skill. You add your roll to your skill and need to reach some Target.
To calculate the actual target roll for a specific effect you need to locate the proper spell seed or seeds to get the base target Roll. Then go down the list of further modifiers. If your spell is based on more than one spellseed,add the value for the first spell seed, then add to that the amount the other spell seeds are above 10. If you would succeed at a Target Roll of 10, but not at the actual targetroll you need to look at the tables for failures.
For more information about the spellseeds refer to the Spellseed page.
If you can't be bothered calculating your own spells, just take a look at the examples

Blood magic

There might be some situations where you need to do a spell that would be impossible with your skill, even when you use a luck point to get the highest roll and have all the assistance you could get.
In those situations you could resort to what is called blood magic.
With blood magic you can boost your skill by the square root of lifepoints sacrificed (through ritual wounding).
For a succesfull sacrifice, you need a success in a magic roll (you can specialise in blood magic).
But if your not using your own life energy the roll gets done with a modifier of -5 if the blood donor is willing or helpless, or at -10 when done during a fight.
The life-energy that gets sacrificed, can't be healed as long as the spell lasts.
A few things modify the amount of life-points before the square root gets taken:

If the sacrifice dies the amount of points get doubled.

If the donor is a virgin the points get doubled.

if the donor is not sentient(i.e. an animal) the points get divided by 10

Ritual magic

Of course blood magic isn't to everyones taste, and to get the bigger bonuses it can become quite messy.
So as an extra measure you can get a bonus to your skill by using more time.
For casting times of several years it is assumed that 8 hours a day get used for the ritual in question. (if the ritual takes more than a lifetime the worst skill of a ritual leader gets used as a base. All extra assistance gets added to that value before dice gets rolled)

Time used	SkillBonus
1 minute	+1
5 minutes	+2
30 minutes	+3
3 hours	+4
1 day	+5
5 days	+6
1 month	+7
6 months	+8
1 year	+9
5 years	+10
25 years	+11
each additional 25 years	+1 each

Tables for magic difficulty

Add the modifier of following tables together and then subtract the resulting difficulty from the magic skill.

Target Roll	Seed
10	Illusion Levitation
11	Analyze Magic Aura Color Calling Force fields Real invisibility Search Sound Surface Solidness Storing of Magic Temperature
12	Air Break Spell Body Curses/Blessings Deflect Magic Earth Electricity(Magnetism) Fire Light Luck Memory Mind Senses Water
13	Change matter Charging Draining Planeshift Shapechanging Summoning Weather
14	Create matter Destroy matter Life

Quality of magic(Number of charges/Spell Modifier effected)

bad(0)	average(1)	good(2)	great(3)	perfect(4)	each charge improvement by one
-1	0	+1	+2	+3	each +1

Distance (Not for calling or summoning)

Touch	<15 feet	<60 feet	<150 feet	each doubling of distance	No sight
-1	0	+1	+2	each +1	+1 to distance modification

Duration

Seconds (1 combat round)	<1 Minute	<10 Minutes	<1 hour	<1 Day	each tripling of duration
-1	0	+1	+2	+3	each +1

Spells that do instant effects, do those effect each combat round when they have a duration.

Area

1 Target	<15 feet radius	<30 feet radius	<100 feet radius	each doubling of the radius
0	+2	+3	+4	each + 2

Abilityscores (Strength for levitation, or change of existing Abilityscores...)

0	1	2	3	each additional +1
0	+1	+2	+3	each + 1

Amount of Change/Precision of planeshifting/Loudness/Clearness of Sound...

Nearly nothing Same world whispering(<20 dB) noise	little within 10,000 miles human speech(<50 dB) Animal sounds	some within 1,000 miles shouting(< 75 dB) words	noticeable within 100 miles <100 dB specific voice	extreme within 10 miles <150 dB singing	incredible within 1 mile <200 dB perfect music	each halfing of off distance each additional 50 dB
-1	0	+1	+2	+3	+4	each +1

Damage dealt by direct effects/stopped by forcefields

1 Point	Willpower points	2* Willpower points	3*Willpower points	each increase of multiplier by one
0	+2	+4	+6	each +2

Change of Weight

< 1 ounce	< 2 pound	< 20 pounds	< 100 pounds	< 200 pounds	each aditional 1000 pounds
0	+1	+2	+3	+4	each +1

Special qualities

5 Points	10	20	40	each additional 20 points
+1	+2	+4	+8	each +4

Note that this is total points of Qualities, not ranks in the Skill like value of the same name. Also you do not get point breaks for drawbacks(or point breaks for limitations). On the contrary you have to pay for those just like you have for beneficial things. Exception to that rule is shapechanging into a specific being. In that case you have to copy the exact special qualities of the target and the amount of quality points is considered to be 20 times the special quality rank of the being in question.

Spellseed page.
Description of spellfailures
Description of some sample spells