Look for an executable file (usually setup_heavenly_heroes_of_antidomi_....exe ). Because it is a GOG release, it is DRM-free and does not require an active internet connection or a launcher to install.
is an RPG developed by Kagura Games and available through GOG.com . The specific file you mentioned, Heavenly.Heroes.of.Antidomi.GOG.rar , appears to be a compressed archive containing the installer for the DRM-free GOG version of the game. Game Overview Heavenly.Heroes.of.Antidomi.GOG.rar
According to the GOG Database, the game has been updated to version v6 (EN 1.01), with a file size typically around 567 MB . How to Use the RAR File Heavenly.Heroes.of.Antidomi.GOG.rar