Okay... well what if he gets a conflicting order? E.g, it's highly likely lucifer said once or twice "Hey, buddy, go up to heaven and kill god for me." But when he went over to god to reap him, God would likely say "Hey, buddy, go down to hell and kill Lucifer for me.". So... what would he do? You imply he wouldn't do anything, but you also effectively said he values Lucifer much more, thus, wouldn't he likely follow through with killing God? If so, what would happen? Did that already happen and God just 'vetoed' it and came back?