So far i know sins can kill all gates but the invurneble gate to the base orcs are in?
Yep. The base in the top right (below existence) is a good base: you can open and close the bridge, which keep sins from running into your base. When faced with two choices just simply flip a coin. Not because it settles the question for you, but because that one second it is in the air you suddenly know what you are hoping for.