The Primarchs could be main characters interacting with her. For example, if she had a vision for the future of the Imperium, she might consult with the more intelligent and far - seeing Primarchs like Guilliman. Another would be the Inquisitors. They are tasked with rooting out heresy and protecting the Imperium, so they could have important meetings with her to report on threats or seek her guidance. And of course, the Custodes. As her personal bodyguards, they would have constant interaction with her in many fanfiction scenarios.
In fanfiction, the Sisters of Battle could be key characters interacting with the female emperor. They are a powerful force dedicated to the Emperor's will. They might receive special orders directly from her or be part of a grand plan she devises. Tech - priests could also be important. The Imperium relies on technology, and she might work with the tech - priests to develop new weapons or defenses. Additionally, the Rogue Traders could interact with her. They explore the galaxy and might bring back valuable information or artifacts that she would be interested in.
A Vampire Lord from a long - lost dynasty could be a main character. He might be trying to reclaim his former glory in the 40k universe filled with so many powerful factions.
The Empress herself is of course a main character. Often, you'll also find Space Marines, as they are a significant part of the Warhammer 40k universe and interact with the Empress in various ways. Imperial Guardsmen may also be present, depending on the plot of the fanfiction.
The traitorous Primarchs or their descendants could also be antagonists. If they believe that the awakened Emperor will bring an end to their own power and influence, they would oppose him. For example, the Night Lords' successors might continue their ways of terror and oppose any attempt by the Emperor to bring order.
One of the main characters is Ciaphas Cain. He is from the 'Gaunt's Ghosts' series. He is a bit of a reluctant hero, always getting into and out of trouble in the most interesting ways.
In Warhammer 50k fanfiction, characters like the Sisters of Battle are quite popular. They are strong, devout warriors, and their stories of faith and combat can be really inspiring. There are also Inquisitors who are often central characters. They have the power to investigate and root out heresy, and their complex personalities, some being more noble and some being more morally ambiguous, make for great storytelling. Additionally, the Ork warbosses can be popular as they bring a lot of chaotic and violent energy to the stories.
Horus Lupercal is a very popular character. His fall from grace and the events leading up to it are often the focus of fanfictions. Another popular one is Magnus the Red. His connection to the warp and his attempts to warn the Emperor make for great story material. Also, Leman Russ is popular. His no - nonsense attitude and his relationship with his legion are often explored in fanfic.
There's also Alaitoc. In fanfiction, female Eldar from Alaitoc are sometimes the focus. They are known for their stealth and marksmanship. Stories might revolve around a female Alaitoc ranger on a long - range scouting mission, encountering unexpected threats and having to rely on her wits and skills to survive.
Sometimes, the interactions are based on a need for mutual assistance. A Star Trek ship might find itself in the Warhammer 40k universe and need the help of a local faction to repair their ship. In return, they offer their knowledge or technology. This can lead to some interesting exchanges as the characters from both universes try to understand each other's values and capabilities.
Space Marines can also be main characters. They might be tasked with protecting an STC site or escorting Tech - Priests to retrieve an STC. Their combat skills are crucial in fending off threats.
They can interact in many ways. Sometimes they are enemies, fighting over resources or territory. For example, in some stories, humans might try to colonize a planet that the Eldar consider sacred.