He uses concentration, speech and gestures. The proceeding for a special effect is stored in complicated magic formulas. Every magician has its own set of formulas, which must be explored personally. Casting spells drains the magicians endurance and there is a risk of failure. A spell is a combination of one or more of this plains.
Every open factor increases the basic difficulty.
When a effect for a plain combination is set the magician can't change them in his whole life. The planes are learned as seperate skills. For a spell the worst learned plane is relevant. Then a test against this value is made. Low endurence increases the risk of failure.