Without the multiplayer there's OpenMW: https://openmw.org/en/ https://openmw.org/en/ Without the open world there's DarkPlaces (based on Quake), with games li

Without the multiplayer there's OpenMW: https://openmw.org/en/ https://openmw.org/en/ Without the open world there's DarkPlaces (based on Quake), with games like Xonotic: https://en.wikipedia.org/wiki/Xonotic https://en.wikipedia.org/wiki/Xonotic Both are really good considering it's hard to make something like this tbh. Not sure if there's anything good that has all 4 of those things, though ;). People often underestimate just how much work game engines are. And also how useless they are without an actual game on them.