Tome of Stoyu

Found by Harpin Falconhand in Korint.

An ancient tome, slight enough to fit snugly in one hand. Its cover, coarse as a duergar’s beard, is dark enough to drink any light careless enough to wander near. A lone sigil, drawn with ink like burnt mercury, looks to crawl across the front. When you rest your hand on the cover you feel a languid shiver. Dark leather straps keep it closed securely. When opened, the pages inside, cold to the touch, appear virginal to anyone but you.

This tome, along with anything written on its pages, can't be damaged by fire or immersion in water. In addition, it doesn't deteriorate with age. However, it cannot be replaced or recovered by ceremony.

As long as you own the Tome of Stoyu and are attuned to it, it has the following properties.

Cyclopean Gaze Besides being your Book of Shadows, you can use the Tome of Stoyu as a spellcasting focus for your warlock spells.

Book of Ancient Secrets As long as you own the Tome of Stoyu you are considered to have the Book of Ancient Secrets Invocation.

Otherworldly Whispers You have advantage on Arcana skill checks.

Forbidden Knowledge Once per long rest, you can attempt to gain insight into a topic or question of your choice by spending one hour studying the Tome of Stoyu. Make a DC 18 Arcana check. On a success, you gain a piece of obscure knowledge or insight that could help you in your quest. On a failure, the knowledge you uncover comes at a cost - you gain a random debilitating effect for the next 24 hours as your mind reels from the horrors of what you've learned.