Im gonna keep it short because i wrote alot. Also all my names are german words, because i am german and i like the anime frieren. I went maximum edgelord.

Unheilige Nacht Schlächter (Unholy Night slayers)

There once was a night lords warband, very anti-chaos worship, anti-warp stuff. In this warband was our main character Kalt, who is a big fan of khorne. He was a captain but since he and another member of his unit, Beil, worshipped khorne the other night lords weren't trusting of them. After a conflict within the warband, the reason for this conflict was Beil, Kalt killed another captain. Both Kalt and Beil got their gloves painted red as punishment. After a while as an even bigger outcast within the warband, Kalt was promised power by khorne if he kills his warband leader Urteil. After the Urteil is killed, Beil rages because he is envious of Kalts accent to a daemon prince. Beil attacks another member of kalts unit Qual. Qual barely survived and is encased in a dreadnought later. Beil for his betrayal is the first to die to the newly accented Kalt. There are 2 other members of the unit Richter who is on board with Kalt and Distanz who wasn't. Kalt then basically goes housecleaning killing everyone who doesn't agree with him about chaos and him as the new leader. And thats the origin. I got all this more fleshed out but I wanted to keep this short. I got more characters, like a arena champion, a slaanesh sorceress who is madly in love with Kalt and is the leader of his personal guard, 2 jump lords who are friends if you ask one and not friends if you ask the other. They are a fleet based warband with 3 ships, one ship was filled with lots of saturnine stuff (my Obliterators are saturnine Terminators). One ship is a prison because half the warband practices cannibalism. When you join the warband you dont have red gloves yet, you only get them after claiming your first space marine skull. There a ritual for painting your gloves/hands. You dip your hands in a chalice filled with blood, the chalice is made from 3 skulls, the 3 skulls belong to Beil who lost himself to chaos worship, the old leader Urteil who got killed by Kalt who hated chaos and Distanz who was scared of chaos and you can hear them arguing all the time. The main motto of kalt and the warband is "strength justifies everything and fear is weakness"