I got a tad sceptical, convinced there's a crapload of beasts in Slavic mythos, and it turns out I was dead wrong. The list of entries in Polish Bestiary contains mostly things explicitly named as demons, in the classical Greek sense of it. There's also a bunch that was either unclear (I'm pretty damn sure Leshi (210) is Russian and we call him Boruta, which is notoriously used in place of the devil in folk tales) or clearly borrowed from some place else (Strzyga is a clearly the same as Strigioi, down to etymology). Not all entries sit undisputably well with my, admittedly eclectic, knowledge.
Still, impressive and enthralling. My bellyaching is by no means intended to ruin the joy or diminish anything.