If we look at it closely, the Batfam's abilities are mostly based on technology and intense physical training. For example, Nightwing's acrobatic skills combined with his martial arts training. In contrast, the characters in Black Butler have more supernatural elements. Sebastian can teleport and has inhuman reflexes. However, they could work together. Batman could use his detective skills to figure out the motives of the Black Butler characters, while Sebastian could use his powers to help the Batfam in combat situations. And Ciel could use his strategic mind to plan operations against their common enemies.
Sebastian's superhuman strength, speed, and demonic powers would be a huge asset in Gotham. He could easily take on many of the thugs and villains. Batman, on the other hand, with his detective skills and gadgets, would be very intrigued by Sebastian. Alfred's combat and medical skills might be similar to some of the skills in the Black Butler world. Ciel's intelligence and strategic thinking could also be useful in Gotham's complex criminal underworld.
Kagome's spiritual arrows could be enhanced by Grell's death scythe in a strange way. Maybe their combined powers could create a new weapon or a powerful blast that could defeat a very strong foe. Also, Shippo's illusions could be used to deceive the enemies, and Bardroy's explosives could be set off at the right moment to create chaos among the enemy ranks, which would give Inuyasha and the Black Butler characters an advantage in battle.
The Akumas in D Gray - Man are created by the Millennium Earl. If Akumas were to enter the Black Butler world, they would be a major threat. Their ability to transform and their inhuman strength would be a challenge for the Black Butler characters. On the other hand, Sebastian's demonic powers and his ability to make contracts could potentially be used to manipulate or destroy the Akumas. The D Gray - Man exorcists are trained to fight Akumas specifically, so their skills would be very useful in this new setting. But the Black Butler characters' knowledge of the local environment and their own unique skills, like Mey - Rin's sharpshooting and Bardroy's combat experience, could also contribute to the fight against the Akumas in ways the D Gray - Man exorcists might not expect.
Well, Superman's strength and invulnerability would be a great match against the brute force of some of the larger Warhammer creatures like Ogres or even some of the daemons. His heat vision could also be a useful weapon against hordes of enemies. Batman's strategic mind would be invaluable in dealing with the complex politics and power struggles in the Warhammer universe. He could also use his gadgets to adapt to the different technologies and magics there. Wonder Woman's combat skills and her Lasso of Truth could be used to great effect in dealing with the more devious characters in Warhammer, like the Dark Elves.
The werewolves in Twilight have their own set of abilities like enhanced strength and pack telepathy. Inuyasha also has his encounters with wolf demons. In a fanfic, the werewolves could team up with Inuyasha against a common enemy, perhaps some powerful demon that has made its way into the Twilight universe. Their combined strength and abilities could create a really dynamic and action - packed story.
A great plot idea is that the reapers from Black Butler somehow cross over to Gotham. They start interfering with the natural order there, which catches the attention of the Batfam. The Batfam initially mistakes them for some new, super - powered villains. Meanwhile, Sebastian is following the reapers to bring them back to their own realm and gets tangled up with the Batfam in the process. And what if Ciel was sent to Gotham on a mission by the Queen and he has to work with the Batfam to complete it.
Naruto's ability to use chakra and perform ninjutsu like the Rasengan could be combined with Hercules' brute strength. For instance, Naruto could use his chakra to enhance Hercules' strength even further, or Hercules could use his strength to create a more powerful impact when Naruto uses his jutsu. Maybe Naruto creates a Rasengan and Hercules throws it with his superhuman force.
The characters would have some really interesting interactions. For example, Sebastian would likely be polite yet calculating when dealing with the Sohma family. He might see them as an interesting study, especially those with the animal curse. Tohru, being her kind self, would probably try to befriend Ciel and the others. However, Ciel might be initially suspicious of her overly - nice demeanor, as he's used to a world full of deception.
Well, Batman is very brooding and serious, while Tony Stark is more flamboyant and sarcastic. Their personalities could clash at first. But they might also learn from each other. Batman could learn to be a bit more open - minded from Stark, and Stark could learn the value of Batman's intense focus. On the other hand, characters like Captain America and Dick Grayson might blend well. They both have a sense of honor and a strong moral compass. Cap could appreciate Dick's acrobatic skills and positive attitude.
Well, Naruto's Rasengan could potentially be infused with black lightning. Imagine a Rasengan crackling with black lightning energy, making it even more destructive. It would be a powerful combination of Naruto's chakra control and the unique energy of black lightning.
The interactions would also depend on the setting of the crossover. If it's set in the world of Black Butler, the Soul Eater characters would have to adapt to the Victorian - era society. Maka, for instance, might be frustrated by the strict social norms while trying to hunt for kishin eggs. The Black Butler characters would be in charge and would likely view the Soul Eater characters as outsiders at first. However, as they work together against common threats, they would start to understand and respect each other. If it's set in Soul Eater's Death City, the Black Butler characters would be in a more modern and chaotic environment, which would be a big change for them.