Originally Posted by
MaxToreador
Concerning the Night Lords, as simple as I can make it, were sent to the DSM for 2 reasons:
#1 What made them unique as a legion. Curze and his legion as a whole believed in both peace through fear of absolute punishment and in absolute corruption. Literally they were Hell; if you even thought of betraying the Imperium you WOULD receive the harshest punishment they could think up. To them there was no escape, they would find you eventually. The kicker being they knew no one was without corruption, it was just a matter of time. This all being the case they were perfect for quelling an Astartes rebellion as their harshness gauge is permanently set to 11 and they would not question that an Astartes (even a Primarch) could fall unlike all the other legions. In a way they always were chaos (lil c) and believed in Chaos even if they didn't know a damned thing about warp creatures and Daemons.
#2 Konrad was already on the penance train right behind Magnus, due to the whole 'we're so metal that when we pass through a system forgeworlds shut down to let their workers have a last day with their families just in case we're cranky' thing. Two birds, single stone mindset. They stop the traitor legions while sustaining heavy losses? Fine, gives the galaxy some time to recover and makes the Emp's job of bringing the NightStalker to heel a little easier.
As to Their Fall:
The folly was in that Nostromo's #1 son was never as close to his dad as the rest of his kin were and saw this ****e coming. Plus the Magnus isn't the only psyker primarch issue, as Grimdark Batman can apparently see the future too bit. So what's a guard dog who's bit too many candy thief's hands off too do? Hatch a long winded plan to teach dear old dad that the Night Lord way was right that requires his own murder-suicide. In the end he knew he and his legion were hypocrites, their own punishment staved off till everyone else's could be dished out.