A character with the Magician Advantage knows a set number of spell effects from the beginning at character creation. The number of spell effects the magician knows how to perform is equal to ten percent of that character's Intellect, rounded down. The character may only cast spells using Spell Effects that he knows unless he is reading the spell directly out of a book. The magician may not switch out these spell effects at any time... once they are memorized, they are there.
A character may increase the number of spell effects he can recall, however. The first method is by increasing the character's Intellect to the next amount where this would be possible. For example, going from 70 Intellect (7 spell effects) to 80 (8 spell effects). Also, every five ranks you increase in any of your Magick skills increases the number of spell effects you know by 1. You do not have to choose your new spell effect immediately, but as soon as you do, you cannot change it.