Viractuth, Serpentine Demoness, , Keeper of Secrets, Locus of the Library, Admonished of the Archives, and most trusted general of Rhyxali, the Queen of Shadows, upon forging the Pact of the Tomb, whispered with it, secrets of Shaddanon.

When defeating certain enemies, there is a chance that the secrets of their souls will become imprinted into your Book of Shadows in the form of rune pages. 

By imbuing one beam from your Eldritch Blast into the Tomb, you may add the secret from a page to the rest of the spell. Upon hitting the target, they must make a WIS Saving throw Each page may be used once per day. Each Eldritch Affliction lasts until the end of your next turn.