New Otherworldly Patron: The Living Library
All over the world, and in many other planes, lay forgotten libraries, buried in the sands of time. These cavernous monuments to knowledge were built by long extinct empire or forgotten archmages who left behind an incredible sum of knowledge in the form of books, scrolls, artefacts and other forms of records. With centuries to themselves, the arcane energy trapped within all of those tomes began to seep into the very structure of the library, spreading from one row to another and intermingling, until the combination of magic energy and knowledge became self-aware.
This new life seeks nothing more than to accrue more knowledge within its halls, and it has selected you as its eyes and ears in the outside world. In exchange for chronicling your experiences, it grants you the skill and power to make it through any adventure.
Borrowing Book
Starting at 1st level, the Living Library allows you to borrow a piece of its collection, its magical knowledge transmitted into your brain by it mere presence. At the end of a long rest, you can perform a ten minute ceremony to conjure a book from the Living Library, making any previously borrowed book return to the Library in the process. When you do, select one of the following books:
Book of Knowledge: When you borrow this book, select two of the following skills of your choice: Arcana, History, Nature or Religion. While you have this book on your person, you gain proficiency in the selected skills (if you do not already have it) and you have advantage to all ability checks where you can add your proficiency bonus from either of the two skill you selected.
Book of the Mage: When you borrow this book, select one of the following cantrips: Control Flame, Dancing Lights, Mage Hand, Mending, or Message. While you have this book on your person, you know the selected cantrip and it is a Warlock cantrip for you. This cantrip does not count against your number of cantrips known
Book of Skills: When you borrow this book, select one skill or tool of your choice. While you have this book on your person, you gain proficiency in the selected skill or tool and your proficiency bonus is doubled for any ability check you make that uses the gained proficiency.
Book of Tongues: When you borrow this book, select a number of languages equal to your proficiency bonus. While you have this book on your person, you understand and speak the chosen languages.
Book of War: When you borrow this book, select two different martial weapons. While you have this book on your person, you have proficiency in the selected weapons as well as proficiency in medium armor and shields.
Expended Spell List
The Living Library grants you a greater selection of spell. When you gain this feature at 1st level, select a school of magic. All spells from that school are added to the Warlock spell list for you.
Fervent Reader
As your relationship with the Living Library grows, it grants you additional access to its content. Starting at 6th level, you can borrow one additional book when you perform the ceremony at the end of a long rest. You can select the same book twice. If you already have borrowed two books and borrow a third one, you choose which of the previous two are returned to the Library. Furthermore, you can now select the following book:
Book of Spells: When borrowing this book, select two Warlock spells. While you have this book on your person, you know the selected spells and they do not count against your number of spells known.
Borrow Energy
You can now tap into the incredible arcane reserves of the Living Library. Starting at 10th level, you can spend 1 minute to contact the Living Library to regain one expended Warlock spell slot. Once you’ve used this ability, you cannot do so again until you finish a short or long rest.
Mystic Secret
The Library grants you an arcane secret. At 14th level, when you finish a long rest, you can choose a different Warlock spell to replace one of your mystic arcanum. The spell must be of the same spell level as the arcanum you replace.