Now digitized, the bestiary is an encyclopedia of supernatural creatures that the Argent family has been keeping since they became hunters. It's 900 pages or so long, and at least part of it is written in archaic latin. The pages on the kanima look like illuminated manuscript.
Gerard keeps the bestiary file on a USB drive on his keys.
For the SDCC 2014, MTV had an artist create a Bestiary to handout to fans.