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i just installed Demigod and i went to play but i found out that it is super laggy, any ideas on what the problem might be and how to fix it?
Laggy in what sense? Is your FPS really low on a system that should be able to handle the game?
If so, you might want to try running the game with the /nosound option. How to do that is described here: http://forums.demigodthegame.com/348389
If this helps, could you please report it in this thread: http://forums.demigodthegame.com/348232 That way we can keep the same issue in one thread and maybe get the dev's attention a bit better.
10 to 15 minutes seems a huge amount of time, have you disabled your AV? I assume you are on the latest version.
Otherwise try /nosound as suggested above