The Grimoire Patron Warlock

Some time after The Fellstar cataclysm, the mages who had protected the people of Chronan from the catastrophic repercussions rose to power, and the mighty Magocracies were born. These nations were ruled with absolute control by those who knew magic, and if you didn't, you were only a puppet to control. The Steaming Age brought an end to the tyranny of the mages, and most of the former rulers were brought down. But the cleverest of them hid their lives' essence and knowledge into their spellbooks, to keep spreading their influence clandestinedly. Any person that came in contact with such a grimoire could be lured by the book's promise of power, and enter a pact to become a warlock for the spirit inhabiting it.

The Grimoire Patron Features

This subclass suits a warlock in pursuit of knowledge, perhaps someone who has failed in their studies to become a wizard. Although the spirit in the grimoire is undoubtedly chaotic, the warlock may choose to oppose it and keep living a lawful life.

1st level: Expanded Spell List, Keeper of the Grimoire, Ritual Casting

6th level: Diligent Student

10th level: Arcane Encyclopedia

14th level: Awakened Arcanum

Expanded Spell List

The Grimoire lets you choose from an expanded list of spells when you prepare a warlock spell. The following spells are added to the warlock spell list for you.

1st level spells: alarm, identify

2nd level spells: arcane lock, detect thoughts

3rd level spells: clairvoyance, intellect fortress

4th level spells: Leomund's secret chest, Mordenkainen's private sanctum

5th level spells: modify memory, Rary's telepathic bond

6th level spell: globe of invulnerability

7th level spell: Mordenkainen's magnificent mansion

8th level spell: mind blank

9th level spell: gate

Keeper of the Grimoire

At first level, you have gained hold of an ancient Grimoire, a tome filled with magical secrets of a deceased mage that are just beginning to unravel to you. The Grimoire is sentient and can talk to you telepathically across any distance and even across planes. The Grimoire cannot be destroyed or taken from you as long as you are alive, as your destinies have intertwined. Any attempt to remove it will lead to the tome teleporting back to your possession. The Grimoire acts as your spellcasting focus.
The Grimoire gives you greater versatility in your choice of spells. You do not learn spells as you level up, but instead prepare spells from the warlock spell list for you to cast. The number of spells you can prepare each day is equal to the number shown on the "Spells Known" column of your warlock class table. The spells you choose must be of a level no higher than your spell slots. Casting the spell doesn't remove it from your list of prepared spells. You can change your list of prepared spells when you finish a long rest. You can also change one of your prepared spells when you finish a short rest.
When you reach 3rd level, you must choose Pact of the Tome as your Pact Boon. The Grimoire will work in place of the Book of Shadows described by the boon, and gain the same properties, except where they contradict with this feature (such as being destructible).

Ritual Casting

At 1st level, you can cast a warlock spell as a ritual if that spell has the ritual tag and you have the spell prepared.

Diligent Student

At 6th level, your study of the Grimoire has steeled your focus and deepened your knowledge. You gain proficiency with Constitution saving throws. You also gain expertise in one of the skills you have proficiency with, doubling your proficiency bonus for that skill.

Arcane Encyclopedia

By 10th level, the secrets written in the Grimoire start opening up to you even more, revealing you information about the surrounding world. If you spend at least 1 minute observing a creature, a place or an object, and succeed on a Intelligence (Arcana) check, your Grimoire will reveal certain information about it:

If it is a creature, you learn its creature type and any damage or condition resistances and immunities it has. The DC is equal to the creature's CR or level.

If it is a place, you learn a brief summary of its history. The DC is 12.

If it is an object, you learn if it is cursed or trapped. The DC is 15.

You can use this feature a number of times equal to your proficiency bonus, regaining all expended uses after you finish a long rest.

Awakened Arcanum

At 14th level, a breakthrough with the Grimoire allows you to use the full scope of your spellcasting potential. You can change the spells related to your Mystic Arcanum features to a spell of equal level from the warlock spell list after you finish a long rest.