You've made a pact with a powerful being that manipulates the weave of magic. A glorious Arch-Mage that has ascended beyond mortality, a creature whose very nature is magic, or even a deity whose portfolio includes spell-craft has chosen you to be their acolyte, channeling their immense knowledge and understanding over the Art to shape the world around you and further their schemes.

Eldritch Grimoire

Your patron bestows upon you an eldritch grimoire, a book capable of holding arcane secrets and magics. At the 1st level choose two 1st-level spells from the wizard spell list to be added to your grimoire. Spells in your grimoire count as warlock spells for you even if they don't appear on the warlock spell list but don't count against the number of warlock spells you know. While you're holding the grimoire, you can cast any spell within it by expending a pact slot as normal, and you can use the grimoire as a spellcasting focus for your warlock spells. When your Pact Magic feature lets you learn a warlock spell of 1st level or higher, you can add another spell of your choice from the wizard spell list to your grimoire, provided the spell is of a level for which you have pact slots, as a maximum of upto 10 spells at any given time. In addition, when you gain a level in this class, you can choose one of the spells you added to your grimoire with this feature and replace it with another spell from the wizard spell list, which also must be of a level for which you have pact slots. If you lose your eldritch grimoire, you can perform a 1-hour ceremony to receive a replacement from your patron. This ceremony can be performed during a short or long rest, and it destroys the previous grimoire. The grimoire turns to ash when you die. If you later gain the Pact of the Tome feature, your grimoire becomes your Book of Shadows.

Manifest Arcanum

At the 1st level, your eldritch grimoire is a conduit of your patron's power and has a number of charges equal to half your warlock level (rounded up). While holding the grimoire, you can can cast a spell in it with a level equal to or lower than half your proficiency bonus (rounded up) by expending a number of charges equal to the spell's level. Your grimoire regains all expended charges when you finish a long rest.

Eldritch Arcana

The more you tug on the weave of magic, the more you can connect with your patron. At the 6th level, while you maintain concentration on a spell, you gain a bonus equal to your Charisma modifier to your Constitution saving throws to maintain concentration on spells. You gain 10ft movement speed. In addition, your patrons bestows upon you his Arcane knowledge, granting you proficiency in Intelligence saving throws.

Spell Turning

Starting at the 10th level, as a reaction, when a creature you can see within 30 ft casts a spell of level equal to or lower than 5th level, you can turn it against a creature of your choice within the same range. This can be done a number of times equal to half your proficiency bonus rounded down. To successfully turn a spell, you must roll a Charisma check with your spellcasting modifier against a DC equal to 10+2xspell level.
In addition, Once per turn, one enemy affected by your spells takes additional damage equal to your Charisma modifier from a single damage roll, provided the spell has an attack roll/saving throw.

Arcane Mastery

Starting at the 14th level, as a bonus action, you sense the presence of magic within 30 feet of you. If you sense magic in this way, you can use your action to see a faint aura around any visible creature or object in the area that bears magic from the Wizard spell list, and you learn its school of magic and names of the spells cast, if any. If the spell is not part of the Wizard spell list, you can only verify the presence of magic in the region. The spell can penetrate most barriers, but it is blocked by 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt. You can use this feature a number of times equal to 1 + Charisma modifier times. You gain all expended uses when you finish a long rest.

Furthermore, you have resistance against the damage of spells.