One exciting plot twist could be that the Chaos forces from Warhammer somehow corrupt a member of the Justice League. Imagine Superman, under the influence of Chaos, turning against his comrades. It would create a huge internal conflict within the League as they struggle to save him without harming him. Another could be that the technology or magic from Warhammer is introduced to the DC Universe in a way that changes the power dynamics. For example, the Warp magic could give new abilities to some of the villains, forcing the Justice League to adapt quickly.
A really cool plot twist could be that the Green Lantern Corps discovers that the Warhammer universe's psykers are a new form of sentient life with a connection to the emotional spectrum. This could lead to a whole new arc where the Green Lanterns try to incorporate these psykers into their ranks or protect them from those in the Warhammer universe who would use them for evil. It would also open up new ways for the Justice League to interact with the Warhammer world.
Perhaps a plot twist where the Imperium of Man teams up with the Justice League against a common enemy, like Darkseid who has somehow made a pact with some of the more malevolent forces in the Warhammer universe. This would be interesting as the two groups have very different ethics and ways of operating. The Imperium's extreme measures might shock some of the more morally upright members of the Justice League, but they would have to find a way to work together for the greater good.
Perhaps a major plot twist could be that the tailed beasts in Naruto are somehow connected to the Mother Boxes in the Justice League world. When the Mother Boxes start acting up, it's because the tailed beasts are influencing them. This would force the Justice League and Naruto's friends to work together to figure out how to stop the chaos. Another plot twist could be that the Justice League members are transported to the Naruto world and have to adapt to the ninja way of life, and in the process, they discover new powers within themselves. And finally, if Naruto was able to summon a Justice League member as a summon, like if he could summon Superman instead of a toad, that would be a wild and unexpected plot twist.
Another great plot twist could be a change in the nature of a well - known hero. In the fanfiction, perhaps Superman loses his powers due to some strange phenomenon in the crossover, and the other members of the Justice League have to step up and protect him while also trying to find a way to restore his powers.
Maybe in the fanfic, there's a villain who can absorb their powers. So when Supergirl and Flash first encounter this villain, they start losing their powers bit by bit. This forces them to rely on their wits and non - superhuman skills to outsmart the villain and find a way to regain their powers before it's too late.
One exciting plot could be that Thanos teams up with Darkseid. The Avengers and Justice League initially misunderstand each other's motives while trying to stop this powerful alliance. They end up in battles among themselves until they realize they need to work together. Iron Man and Batman could be the first to figure it out, using their intellects to analyze the situation.
A cool plot could be a time - travel related crossover. The Young Justice team travels back in time and meets the younger versions of the Justice League members. They have to work together to stop a time - traveling villain from changing history in a way that would destroy the future. Or perhaps there's a magic - based crossover where a powerful sorcerer is causing chaos. The Justice League, which is more used to physical threats, has to team up with the Young Justice, some of whom have magic - related powers, to defeat the sorcerer.
One exciting plot twist could be that the Infinity Stones have a different origin in this fanfic. Maybe they were created by an ancient race that both the Avengers and Guardians have to discover together. This would force them to work closely and share their knowledge.
One idea could be that an ancient, powerful enemy emerges that the Justice League alone can't handle. Supergirl, with her unique Kryptonian powers and different perspective, joins them. She might introduce some Kryptonian technology or fighting techniques that give them an edge. For example, she could have a device that can neutralize the enemy's energy - based attacks.
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.
Well, a plot twist could be Batman's technology being hacked by an unknown enemy. Since he is known for his high - tech gadgets and strategies, if his systems were compromised, it would put the whole Justice League in jeopardy. Maybe the hack reveals some of Batman's deepest secrets, which could either cause a rift within the League or bring them closer together as they deal with the fallout. Another idea is that Batman discovers a long - lost relative who has ties to one of the Justice League's main enemies. This would create a moral dilemma for Batman and add a whole new layer of complexity to the story.
One exciting plot twist could be the discovery of a hidden connection between Smallville's Clark Kent and The Flash's Barry Allen that predates their superhero identities. Maybe they are related in some way through their alien or metahuman genetics. Another could be a villain who has the ability to manipulate time and space, causing chaos in both Smallville and Central City. This would force Clark and Barry to work together in ways they haven't before. A third plot twist might be that a character from Smallville who was thought to be normal actually has latent superpowers that are activated during the crossover, adding an unexpected element to the story.