A creature of Faerie with a strange perception of humor.
The Tome has transparent, ethereal pages, the writing is only visible to the Tome's owner. In spectral form, they can grow a large toothy maw to consume the souls/spirits of other living creatures, these are the components to their spellcasting and are expended when they use their Tome.
Keep or change whatever you like, really. Just some inspiration I got while drawing them.
Loosely based on the [x] asiatic lily
edit; symbols are from the Cistercian monk numeral system, a very simple number system. The symbols are not specific, they just look quite fantastical, do they not?