This is libxayagame compiled for Windows as a static DLL along with its dependencies. The libxayagame DLL is libxayawrap.dll. Everything is inside the "XayaStateProcessor" folder.

If you're using C#, you'll need XAYAWrapper as well. It's packaged in the same download as XayaStateProcessor.

The download can be found inside the xayalib_unity repository.