Sea of ​​Despair? But I have the Legiones Astartes

[Explosive troops, behind-the-scenes, group portrait, no female protagonist, myriad races in the universe, protagonist first, start as an Astartes] Journey through humanity's most vulnerable and hopeless universe to become a member of a hive surviving in the cracks of the underworld of Kandal. Shortly after crossing over, you encounter the Bloody Hands, the hive's largest gang, coming to collect grain. What should you do when a group of ruthless executioners invade the civilian area? [Bang, master, don't be afraid. The barracks system has been activated for you.] [Bang, the system has opened a space in your mind for unlimited barracks placement.] [Bang, congratulations to the master for acquiring a thousand Greyhound Space Marines from the Salamanders, the 18th Legion in Warhammer 40,000.] [Bang...