One idea could be a story about a Dark Eldar wych who is trying to rise in the ranks within her cult. She could face challenges from rival wychs and have to prove her worth in the gladiatorial arenas of Commorragh.
They fill in many gaps in the lore. For example, they show how different legions were formed, their initial ideologies, and what led them to their current states. Novels like 'Horus Rising' are crucial as they start to build the foundation of the great conflict that is the Horus Heresy.
These novels are really important for the Warhammer 40K lore. They provide in - depth stories about the characters who are part of the Dark Heresy setting. For instance, we get to see how the Inquisitors operate, what their motives are, and how they deal with threats. They also introduce new storylines that can be picked up and developed further in other parts of the Warhammer 40K universe. The novels can even change the way we perceive certain races or factions, as they might show a different side to them that we haven't seen before.
Well, for a simple start, you could write about a Dark Eldar Kabalite warrior's journey. He might be sent on a mission to capture a valuable psyker from a human world. It would be full of action as he battles the Imperium's forces protecting the psyker.
A great read is 'The Kabal of the Black Heart' novel. It focuses on a particular Kabal within the Dark Eldar. It shows their relationships with other factions in the Warhammer 40k setting, their thirst for power, and the dark magic and technology they use. This novel gives a detailed look at their military strategies and the internal politics of the Kabal.
One interesting story could be about a Dark Eldar raid on a Imperial outpost. They swoop in with their fast ships, taking the Imperials by surprise. They capture slaves and valuable resources, leaving destruction in their wake.
One of the great ones is 'Fulgrim'. It gives deep insights into the character of Fulgrim and the fall of his legion. Another is 'Horus Rising' which sets the stage for the Horus Heresy, a crucial event in the Warhammer 40k universe. 'The First Heretic' is also important as it delves into the roots of the Chaos influence on the Word Bearers legion.