To gain access to spells, casting classes must spend a certain amount of time preparing them. The below table gives these times:
Characters who spend less than the required time in preparation will only be able to use spells up to the level that they have spent time for. E.g., if a ninth level magic user is interrupted after half an hour spent in preparation, he would only have access to 1st through 3rd level spells, not his 4th and 5th level ones. To gain them, he has to start the entire process over.
Characters always have access to 0th level spells, and arcane casters do not need to devote spell slots to their preparation.
Divine casters (Clerics, Druids, Paladins, and Rangers) acquire their spells through committing their own power to gods, through prayer. The gods then grant them access to a portion of their power for casting spells. These spells do not have to be preselected at the time of prayer.
Arcane casters (Magic Users and Bards) derive the power of their spells through their own life force. Their preparation time involves committing their own life force into gemstones to be later called out to cast their spells. This requires the caster to preselect which types of spells to use at the time of preparation. A table describing the gemstone requirements for casting is shown below.
For practical purposes, the magic user is assumed to be carrying sufficient gemstones on his person to power all of his spells, however in certain circumstances, this mechanic could become necessary.