I Was Supposed to Become a Knight, So What's with These Astartes?

My name is Luo Xia, and I am utterly loyal to the Emperor. An accident sent me transmigrating! The good news: I’ve arrived in a world of swords and magic, wizards and knights, dwarves and elves. It even has supreme gods and demon gods enthroned high above! But the bad news! This is absolutely not Holy Terra, the sacred world I’ve dreamed of protecting with my life! “Chovy! If I’m going to transmigrate, at least send me somewhere good!” “I want to be a Space Marine, an Astartes! Who wants to be a knight?!” 【Welcome to Warhammer 40K】 【I have to say, you’re a lucky one. Your absolute loyalty caught the Emperor’s attention, and after your death, he summoned you to the world of Warhammer 40K.】 【This is a world of roaring chainswords, surging psychic power, wars between interstellar races, and the rampaging Chaos Gods of the Warp!】 【Sounds dangerous, right?】 【So if you want to stay alive, do your best to become an Astartes!】 “Huh? Is this System legit?” 【Oh my god! An evil daemon of Slaanesh has escaped from the Warp! As an Astartes warrior charged with upholding loyalty and honor, defeat her! Let the Emperor witness your loyalty!】 【Quest rewards: 1 Ultramarines gene-seed, 800 Emperor’s Honor points, and increased resistance to Slaanesh daemons.】 Luo Xia looked at the exotic black-stockinged witch sprawled beneath him and swallowed hard. “Who said this System was lame? This System is freaking awesome!” P.S. [Glitched System] [Invincible] [Old-school cultivation immortal]