For the full game, official downloads are managed through digital storefront clients rather than standalone zip archives:
A common zip file named Orcs Must Die! 3_1002_gamesave.zip was used by players to transfer progress from Stadia to Steam. File: Orcs.Must.Die.3.zip ...
Accessible via the PlayStation Store and Xbox Store . Guide :: Beyond OMD3: Mods and Modding - Steam Community For the full game, official downloads are managed
Depending on where you found the file, it likely serves one of these purposes: For the full game