I've put together a simple black-and-white PDF detailing...
... a very dodgy grimoire - which offers a too-good-to-be-true easy-to-cast spell. And,
... two plot hooks for GMs/SGs/etc. to built into adventures and incidents within an existing saga.
The book described in the PDF is inspired particularly by a grimoire called the Ars Notoria, written in Latin in what is today northern Italy, in the 13th Century, and can be used on its own or within your current stories, or integrated into The House of the Crescent Sun or Medieval Nights.
So if you want an infernal book that will mess with your players...
Currently a free download, here (yes that's a Patreon link; no, for the moment it does not require a subscription).