A possible fanfiction idea could be her journey through the warp. The warp is a dangerous and unpredictable place in Warhammer 40k. What if she ventures into it to gain some kind of knowledge or power? How would she survive the daemons and the other horrors there? Another idea is a time - travel fanfiction. What if she is sent back in time to the early days of the Imperium? How would she change things? And finally, a fanfiction about her facing a new and unknown enemy that challenges her in ways she's never been challenged before.
One interesting idea could be the combination of Naruto's ninja abilities with the high - tech and grimdark elements of Warhammer 40k. For example, Naruto's shadow clone jutsu might be used in a unique way on the battlefields of the 41st millennium. Maybe the clones could be used to infiltrate enemy lines or to overwhelm ork mobs.
One idea could be a crossover with the Star Trek universe. The Tyranids could be seen as an extremely hostile alien force that the Federation has to deal with. Their bio - ships and swarming tactics would be a huge contrast to the more technological - based Starfleet.
One idea could be inserting yourself as a new recruit in a Space Marine chapter. You could experience the brutal training and the strict code of honor. Another is to be a tech - priest, exploring the complex machinery and the religious aspects tied to it. Maybe even be a rogue trader, traveling the galaxy in search of profit and adventure.
One idea could be a vampire Space Marine. Maybe a genetic experiment gone wrong in the Imperium that results in a Marine with vampiric traits. He has to struggle with his newfound thirst while still trying to fulfill his duty to the Emperor.
Another interesting concept is to have a Primarch face a completely new enemy. Not the usual chaos forces or xenos, but something from within the Imperium itself that has turned against it. This would create a lot of internal conflict and moral dilemmas for the Primarch to deal with.
One idea could be a crossover with Star Wars. Imagine the Imperium of Man encountering the Galactic Empire. The two totalitarian regimes could have some intense ideological battles and epic space battles as well.
One interesting fanfiction could be about the Emperor's Daughter having unique psychic powers that she uses to protect a beleaguered Imperial world. In this story, she might face off against chaos cults and use her powers in ways that surprise even the most veteran Space Marines.
Another plot could revolve around a Rogue Trader facing a mutiny on their ship. Maybe the crew has been influenced by a chaos cult or they simply disagree with the Trader's latest high - risk venture. The Trader has to find a way to regain control and deal with the traitors.
A really interesting plot could revolve around the origin of the demons in both universes. The fanfiction could explore if there is a connection between the Chaos demons in Warhammer 40K and the demons in Doom. Maybe the Doom Slayer and a Warhammer 40K Inquisitor work together to uncover this mystery while fending off the never - ending waves of enemies.
One interesting fanfiction could be about a female Eldar ranger on a solo mission to retrieve an ancient artifact. She has to face various xenos threats and navigate through dangerous terrains. In this story, her skills with the shuriken catapult are put to the ultimate test.