Source: Explorer's Guide to Wildemount

Wondrous item, legendary (requires attunement by a wizard)

Several of these spellbooks with gilded pages and silver-plated covers were created during the Age of Arcanum, but only one has been found since the Calamity ended. The book has an infinite number of pages, is three inches thick, eight inches wide, twelve inches long, and weighs three pounds.

Dormant. Most of the book is blank, but the following spells are recorded in the first pages of the tome: Alarm , Antimagic Field , Bigby's Hand , Blight , Charm Person , Confusion , Control Weather , Create Undead , Detect Thoughts , Enlarge/Reduce , Fear , Foresight , Gaseous Form , Glyph of Warding , Legend Lore , Leomund's Tiny Hut , Mass Suggestion , Mislead , Misty Step , Mordenkainen's Faithful Hound , Prismatic Spray , Ray of Enfeeblement , Silent Image , Teleport , and Thunderwave .

You can use the grimoire as your spellbook, and you can scribe new spells into it as normal. When you prepare wizard spells using the grimoire, the number of wizard spells you can prepare increases by 1.

Awakened. When the Grimoire Infinitus reaches an awakened state, it gains the following properties:

• While you carry the spellbook, you have advantage on saving throws against spells and magical effects.
• When you prepare wizard spells using the grimoire as your spellbook, the number of spells you can prepare increases by 1 again.

Exalted. When the Grimoire Infinitus reaches an exalted state, it gains the following properties:

• You can now use your Arcane Recovery feature twice between long rests, rather than once.
• When you prepare wizard spells using the grimoire as your spellbook, the number of spells you can prepare increases by 1 again.