The kanji of the book Ainz gave Fluder was not the YGGDRASIL Book of the Dead but the Egyptian one. Thus, it appears he gave him this occult book to keep him busy. However, due to Fluder having Bishop, Forbidden Arts, and high tier Arcane amounts of Magic classes, he could theoretically link the Divine ritualness of the Book of the Dead to his Forbidden Arts and Arcane disciplines to create new spells that resemble these descriptions. That is, it's a framework for him to develop similar spells using jargon from our world related to souls and what not. So they don't actually exist, but he may able to make them exist in a world with magic.