Exactly what the leviathans were doing until Commander Shepard disturb them.
"If there is a God who rules this world, it is a stern, solemn, and definitely a good being. A being that is far too great. God keeps forcing us to confront these cruel fates. As those were the rules of this world! Oh, God... I'll slice you into tiny pieces and feed you to the pigs! Our battlefield is no place for that piece of shit, God! I think it's time we took over God's work. We, soldiers, will take God's place. Put the arrogant ass, God, out of a job! All right troops... It's time for war!"