One idea could be to combine the unique weaponry of RWBY with the grimdark setting of Warhammer. For example, Ruby's scythe could be enchanted with some sort of Warhammer - style magic or runes. Another idea is to have the characters from RWBY face off against Warhammer - style daemons or chaos warriors. This would really test their skills and teamwork. Also, the concept of semblances could be related to the powers in the Warhammer universe in some way, like a character's semblance being a form of psychic power in the context of Warhammer.
Ruby Rose is often a popular crossover character. Her combat skills and leadership in RWBY make her a natural fit to be inserted into the Warhammer 40K universe. She could potentially lead a squad of Space Marines or be a key figure in a resistance against some of the darker forces. Another popular one is Yang Xiao Long. Her strength and brawler - like combat style can be really interesting when pitted against the various foes in 40K.
Ruby and a Skaven Assassin could be an interesting pairing. Ruby with her speed and scythe skills would be pitted against the sneaky and devious Skaven. It would be a battle of wits and speed. Another great pairing could be Weiss and a High Elf Mage. Weiss's elegance and ice powers could contrast and interact with the Elf's magic. And Yang and a Chaos Space Marine. Yang's brute strength and brawler style against the super - powered and corrupted Chaos Space Marine would make for an intense fight.
Character development is key. If you're bringing in characters from different franchises, make sure they stay true to their original selves while also growing in the new environment. For instance, if Captain Kirk enters the 40k universe, he would be shocked by the brutality but also use his wits to survive. You also need to think about how the different powers and abilities will interact. In a crossover with Harry Potter, how would a Space Marine react to magic? There are so many possibilities to explore.
One great 'Warhammer 40000 Crossover Fanfiction' is the one where it crosses with Star Wars. It's really interesting to see the Imperial Guard facing off against Stormtroopers. The different combat styles and ideologies make for a great read.
The Contemptor Savior in this context might have unique abilities. For example, it could have advanced weaponry similar to what we see in Warhammer. In a RWBY fanfic, it could use these to great effect against Salem's forces. It might also have some sort of shielding or defense mechanism that the RWBY characters could learn from to improve their own combat capabilities.
Well, this kind of fanfiction might be exploring themes that are a bit controversial. It could be that the writer wants to show a different side of the RWBY characters by putting them in a difficult situation like enslavement in the world of Total Warhammer. However, it also depends on how the author handles it. If not done carefully, it could be misinterpreted. For example, if it's too dark and doesn't have any redeeming qualities in the story, it might not be well - received by all fans.
The use of miscommunication is great too. Imagine a group of Imperial Guardsmen trying to communicate with an alien race that has a completely different language and cultural understanding. The guardsmen's attempts to be diplomatic while the aliens are completely misinterpreting everything can lead to some truly laugh - out - loud moments. Also, the cultural differences can be exaggerated for comedic effect, such as the aliens thinking the guardsmen's helmets are part of their mating rituals or something equally absurd.
Ruby Rose is often quite popular. Her speed and scythe - wielding skills can be very interesting when translated into the Warhammer universe. Another popular one is Yang Xiao Long, with her powerful punches and her fearless attitude. In the Warhammer context, she could be a force to be reckoned with.
One interesting concept could be the combination of RWBY's unique semblances with Warhammer's vast array of powers and races. For example, seeing a character from RWBY use their semblance in the context of a Warhammer battle. Another concept might be the exploration of how RWBY characters would adapt to the often darker and more brutal world of Warhammer.