Divine spellcasters prepare their spells in largely the same manner as wizards do, but with a few differences. The relevant ability for divine spells is Wisdom.
To prepare a divine spell, a character must have a Wisdom score of 10 + the spell’s level. Likewise, bonus spells are based on Wisdom.
Time of Day: A divine spellcaster chooses and prepares spells ahead of time, just as a wizard does. However, a divine spellcaster does not require a period of rest to prepare spells.
Instead, the character chooses a particular part of the day to pray and receive spells. The time is usually associated with some daily event.
If some event prevents a character from praying at the proper time, he must do so as soon as possible. If the character does not stop to pray for spells at the first opportunity, he must wait until the next day to prepare spells.
Spell Selection and Preparation: A divine spellcaster selects and prepares spells ahead of time through prayer and meditation at a particular time of day. The time required to prepare spells is the same as it is for a wizard (1 hour), as is the requirement for a relatively peaceful environment.
A divine spellcaster does not have to prepare all his spells at once. However, the character’s mind is considered fresh only during his or her first daily spell preparation, so a divine spellcaster cannot fill a slot that is empty because he or she has cast a spell or abandoned a previously prepared spell.
Divine spellcasters do not require spellbooks. However, such a character’s spell selection is limited to the spells on the list for his or her class.
Adepts, blackguards, clerics, druids, paladins, and rangers have separate spell lists. A cleric also has access to two domains determined during his character creation.
Each domain gives him access to a domain spell at each spell level from 1st to 9th, as well as a special granted power. With access to two domain spells at each spell level - one from each of his two domains - a cleric must prepare, as an extra domain spell, one or the other each day for each level of spell he can cast.
If a domain spell is not on the cleric spell list, it can be prepared only in a domain spell slot.
Spell Slots: The character class tables show how many spells of each level a character can cast per day.
These openings for daily spells are called spell slots. A spellcaster always has the option to fill a higher-level spell slot with a lower level spell.
A spellcaster who lacks a high enough ability score to cast spells that would otherwise be his or her due still gets the slots but must fill them with spells of lower level.
Recent Casting Limit: As with arcane spells, at the time of preparation any spells cast within the previous 8 hours count against the number of spells that can be prepared.
Spontaneous Casting of Cure and Inflict Spells: A good cleric (or a cleric of a good deity) can spontaneously cast a cure spell in place of a prepared spell of the same level or higher, but not in place of a domain spell. An evil cleric (or a cleric of an evil deity) can spontaneously cast an inflict spell in place of a prepared spell (one that is not a domain spell) of the same level or higher.
Each neutral cleric of a neutral deity either spontaneously casts cure spells like a good cleric or inflict spells like an evil one, depending on which option the player chooses when creating the character. The divine energy of the spell that the cure or inflict spell substitutes for is converted into the cure or inflict spell as if that spell had been prepared all along.
Spontaneous Casting of Summon Nature’s Ally Spells: A druid can spontaneously cast a summon nature’s ally spell in place of a prepared spell of the same level or higher. The divine energy of the spell that the summon nature’s ally spell substitutes for is converted into the summon spell as if that spell had been prepared all along.
