A spellbook is a list of magic spells available for casting to a player. There are currently four spellbooks: the standard/modern spellbook, the Ancient magicks spellbook, the Lunar spellbook and the Arceuus spellbook. A player may only cast spells from their current spellbook, and if they wish to use spells from another spellbook they must change to that spellbook.
It is possible to switch to and from the Ancient Magicks spellbook and Lunar spellbook, without switching back at the former altar. For example, it is possible for players who are on Ancient Magicks to pray at the Astral Altar, where their spellbook will switch to Lunar. If players wish, they may pray again to deactivate the Lunar spellbook and get their spellbooks switched to Modern.
The standard spellbook, also known as the modern magic spellbook, is available to all players, whereas the other spellbooks can only be unlocked through members quests.
This spellbook contains the most spells (66), as well as the most types of spells; offensive, skills, enchanting and teleportation.
The Ancient Magicks spellbook is composed of offensive and teleportation spells. It becomes available to players after they complete the Desert Treasure quest.
To change to the Ancient Magicks spellbook, or back from the Ancient Magicks to the standard spellbook, players must enter the Jaldraocht Pyramid in the desert south of Al Kharid and west of Pollnivneach from the rear and pray at the altar. The Ancient Magicks are considered the most powerful and dangerous spells in Runescape due to their high hits and special capabilities.
The Lunar spellbook contains no offensive spells. They are filled with defensive, self-help, skill-related and utility spells.
The Lunar spellbook becomes available to a player after completion of the Lunar Diplomacy quest. More Lunar spells can be unlocked after completing Dream Mentor. To change to the Lunar spellbook or back from the Lunar to the standard spellbook, a player must pray at the Astral Altar on the south-east side of Lunar Isle.
The Arceuus spellbook contains no offensive spells.
The Arceuus spellbook becomes available after reaching 60% favour with the Arceuus in Great Kourend within Zeah. To change to the Arceuus spellbook, players must speak to Tyss by the Dark altar, north of Arceuus.
The book contains 22 different monsters that can be reanimated with their respective ensouled head, which are dropped by monsters of the same type.