Prerequisite: Pact of Tome

Your tome becomes infused with eldritch powers of your Patron. Whenever you are casting warlock spells, you can consider your tome as a spellcasting focus.

Also, you can add Charisma Modifier to damage rolls made by cantrips granted by Pact of Tome. You can not add Charisma Modifier to damage rolls if cantrip already has it.