Astalon: Tears of the Earth

Underneath the very first elevator room (Gorgon Tomb 1), there's a blue door. Enter this door to find a purple bat creature, which gives you your bestiary. You can see this by pausing, then pressing Y.

You need to reach "Completed" 42/84, and then go back to the purple bat. It won't pop if you're just wandering around.

There's a full bestiary here: https://steamcommunity.com/sharedfiles/filedetails/?id=25088...

Even better, it includes a map showing where to find any enemies you still need to max out. (for me, most were in Ruins of Ash, but your mileage may vary).

The Bestiary and Map belong to Demajen, who does amazing guides for Metroidvanias: https://steamcommunity.com/id/demajen/myworkshopfiles/?secti...

If you want to thank him -- buy him a coffee at https://ko-fi.com/demajen