The novels also focus on the internal struggles within the Imperium. There are power plays, different factions vying for control, and the challenges of maintaining order in a universe filled with chaos. For example, the different Space Marine Chapters may have different views on how to deal with the emerging threats, which causes some tension.
The antagonists from the forces of Chaos are also key in a way. Characters like the Chaos Lords or daemonic entities create the conflict. Their actions and plots drive the story forward as the Imperium has to counter their threats. Their motives of spreading chaos and destruction set the stage for the intense battles and struggles in the novels.
The story of Warhammer 40k Dark Imperium is centered around the Imperium of Man at a very crucial time. Guilliman, a significant figure, has resurfaced. His return shakes things up as the Imperium has been in a rather dire state. There are the forces of Chaos constantly attacking from all sides. Guilliman tries to bring order back to the Imperium, which has been fragmented over time. The plot also shows how the Imperium's military forces, especially the Space Marines, adapt to the new leadership and the challenges that come with it. It's a story full of battles, political intrigue within the Imperium, and the never - ending fight against Chaos.
It's mainly about the Imperium of Man in a dark and complex setting. It delves into the politics, wars, and various factions within the Imperium. There are power struggles, battles against alien threats, and the exploration of the dark secrets that lurk within this vast galactic empire.
As I don't know the specific 'imperium real story', I can't say for sure what the main characters are. They could be emperors, generals, or ordinary people who play a crucial role in the development of the imperium.