Tome of Sedar
Found by Zayn is his backpack when it was handed back to him in the Kasarian Embassy in Banak.
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 Sedar and are attuned to it, it has the following properties.
Cyclopean Gaze Besides being your Book of Shadows, you can use the Tome of Sedar as a spellcasting focus for your warlock spells.
Book of Ancient Secrets As long as you own the Tome of Sedar you are considered to have the Book of Ancient Secrets Invocation.
Eyes of the Elders You have advantage on Investigation skill checks.
Revelations of Averoigne The tome allows you to try to cast a cantrip that you don't know. The cantrip must be on the warlock spell list, and you must make a DC 15 Arcana check. If the check succeeds, you cast the spell. If the check fails, so does the spell, and the action used to cast the spell is wasted. In either case, you can't use this property again until you finish a long rest.
Incomprehensible Knowledge Once per long rest, you can attempt to cast a warlock spell without expending a spell slot. However, doing so carries a risk - you must make a DC 20 Wisdom saving throw or be afflicted with a random form of madness for 1d4 hours. The madness effect ends early if you take damage.
Dark Mage’s Tome Once per short rest, you can use your bonus action to summon a book mount, it can be dismissed as a free action. It can only be summoned when you are not entangled, grappled or otherwise compromised. The mount appears as an open book of six feet by four feet, it’s purple cover faced towards the floor. It hovers a meter off the ground with you seated upon the open pages when summoned. It won’t accept any other rider than you and does not have room for passengers but has a 480 lb. carrying capacity. As long as you remain on the mount, you have a float movement speed of 40 feet instead of your usual walking speed. The Dark Mage’s Tome cannot change its float height but it is able to cross any gap if it can do so within one round, otherwise it falls. You take only half falling damage when riding this mount. It has twenty hit points, when those are lost, the mount disappears and you won’t be able to summon it again until after a long rest.