"'Tis the darkest Glyph thou bearest. It sacrifices stray souls to summon unearthly force. Unearthly force shall obey and serve thee. 'Tis named 'Chaos Legion'."

If you are writing for a tabletop army or fan fiction, these fit the "Chaos Space Marine" aesthetic:

“I love the Night Lords for their terror tactics—they don't like the Imperium or Chaos, they just have a neat story.” Reddit · r/Spacemarine · 7 months ago

In a world of shadows, the only weapon against darkness is the legion of demons you command.