Returns a Spellbook spell card back to the deck for later use.
Returning to deck is not a good form of retrieval.
This monster’s boost does not go away during the end phase, meaning you can you can stack the boosts indefinitely.
Here are some Spellbook spell cards that support the Prophecy Archetype and Spellcasters in general. Return them to the deck with Strength of Prophecy’s effect for recycling and an attack boost. Use Spellbook of Power and then return it to the deck with Strength of Prophecy. You now have a high attack monster, that can search out Spellbook of Power when it destroys a monster by battle, you can then repeat this every turn.