maplestation_modules/code/modules/client/preferences/spellbook/items/spellbook_entry.dm

/proc/generate_spellbook_items	Generate a list of singleton spellbook_item datums from all subtypes of [type_to_generate]
/datum/spellbook_item	A entry in the spellbook. Can add anything/adjust anything, but should be themed after magic. Only one instance of any given type should exist at a time. These are singleton instances, and are stored in GLOB.all_spellbook_datums, in a assoc list of (entry.type -> entry singleton).