We've gotten several strange crash reports from various users on Windows. Sorry for the inconvenience! It appears that Avast or other antivirus programs are interfering with the startup of the game and cause Windows exceptions to occur, which in turn cause the game to crash.
We're currently not sure why this happens or what we can do about it, so as a workaround you'll have to make sure to whitelist Eternia in Avast or other antivirus software. To find out where Eternia's executable is located, simply right-click its entry in steam, select Manage and Show Local Files.
Note that this does not occur with Windows' built-in antivirus software.