......."That's not to say that the Night Lords aren't pants shittingly terrifying. They know what they're good at, hit and run terrorist attacks, and they stick to it. They've had enough common sense to survive for so long despite having so many disadvantages compared to the other eight legions, so they're probably the most sensible bunch. Of course this is relative to chaos so by sensible we mean "will hang you with your small intestine to cause fear in the enemy" rather than "completely ignore the enemy army to attack a strategically worthless town to make sacrifices for the dark gods." It helps that their attacks are so low-key (except for the bombing a planet one) that the Night Lords are not actively hunted by the Imperium. Otherwise they'd likely be wiped out in short order."