First, choose the two universes you want to cross over. For example, if it's Warhammer 40k and Star Trek. Then, research both universes thoroughly. Know the lore, the characters, the technology, etc. After that, come up with a basic plot. Maybe the Starfleet encounters the Imperium of Man and there's a misunderstanding that leads to conflict at first.
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.
I think Warhammer 40k fanfics are a great way for fans to explore the vast and complex universe further. A good fanfic can add depth to the existing lore. For example, it might focus on the daily lives of the Imperial Guardsmen, which we don't often get to see in the official works. But there are also those that are just not up to par. Maybe they lack proper grammar or have a really convoluted plot that doesn't make sense in the context of the 40k universe.
A specific Warhammer 40k fanfic could either be a masterpiece or a disaster. If it manages to capture the essence of the 40k universe, such as the scale of the battles, the complex politics between different factions, and the religious fanaticism that pervades the Imperium, it's likely to be a good one. However, if it goes against the established canon too much or has a poor writing style, it won't be as appealing.
One great 'Warhammer 40k Emperor Crossover Fanfiction' is the one where the Emperor crosses over into a modern Earth setting. It shows how his powerful psychic abilities and leadership skills shock the modern world.
One idea could be the Imperium of Man encountering the Citadel Council. The Imperium's strict dogma and military might would clash with the Council's more diplomatic approach. For example, the Space Marines might be seen as terrifying super - soldiers by the Mass Effect races.
One interesting concept is the crossover with other popular sci - fi universes. For example, a crossover with Star Wars could have the Imperium of Man facing off against the Galactic Empire. Another concept could be the combination of different Warhammer 40k factions in unexpected ways within the fanfiction. Maybe the Space Marines teaming up with the Orks against a greater threat.
One factor could be overly melodramatic characters. For example, a Space Marine who constantly spouts cheesy one - liners in every situation. Another might be when the fanfic completely misrepresents the lore of the Warhammer 40k universe. If it has a character using technology in a way that goes against the established rules of the setting, it can come across as cringey. Also, bad writing like poor grammar and lack of proper pacing can make a fanfic cringey.
No. Fanfic that involves sexual content is not appropriate as it goes against the general ethics and may also violate the terms of use related to the Warhammer 40k franchise. The Warhammer 40k universe is mainly about epic battles, complex lore, and interesting characters, and should be focused on those aspects rather than inappropriate content.
A bad Warhammer 40k fanfic might have a weak plot. It could be just a bunch of random events strung together without any real purpose or build - up. For instance, the story might start with a battle against the Tyranids, then suddenly shift to a diplomatic mission with the Eldar with no clear connection between the two. Also, bad writing style can contribute. If the prose is overly simplistic or filled with grammar and spelling mistakes, it makes for a not - so - great fanfic.