Pathfinder and dungeons and dragons monster manuals are EXCELLENT for this sort of thing. If you can find a PDF of planescape, that sounds a lot like the setting you are looking at making (where basically EVERY religion is true and the gods hang out with each other and stuff).
The pathfinder SRD has all the books gathered in a single place, and the
bestiary would be a good place to look, as it draws from all sorts of religion and fantasy and myths.
Finally, just as a world building project, take a look at a map, and determine where everything is gathered. Like, where would the largest gatherings of elves be? Would dragons move together in packs, or are they more traditionally solitary creatures? How does each country respond to this issue? There are a lot of global aspects to look at when trying to do something like this. Think about why. You don't have to tell your reader why, but you should probably know why so everything still makes sense from your point of view.