One idea could be to cross Halo Wars with another popular sci - fi franchise like Star Trek. Imagine the Covenant and the Federation having to deal with each other. Another idea is to have a crossover with a fantasy world, like Lord of the Rings. Maybe the Spartans end up in Middle - earth fighting alongside the elves and dwarves against a new threat that has elements of the Flood. A third idea could be a crossover with a post - apocalyptic world. The Halo Wars units could be trying to survive in a world full of mutants and scarce resources.
Well, you could do a time - travel based 'halo wars crossover fanfiction'. For example, some Halo Wars characters could be sent back in time to a crucial moment in human history and they have to change things without disrupting the timeline too much. Or, you could have a crossover where the Halo Wars universe merges with a cyberpunk world. The high - tech weapons of Halo Wars in a neon - lit, dystopian city would be really cool. Also, a crossover with a superhero universe would be interesting. Picture the Spartans teaming up with superheroes to fight an evil force that's a combination of Covenant and super - villains.
Perhaps a group of Spartans could be sent on a mission in the Star Wars galaxy. They get caught in the middle of the Clone Wars and have to decide which side to support. Their unique upbringing and loyalty to the UNSC would create an interesting dynamic as they interact with the political and military factions in Star Wars.
One idea could be that Master Chief somehow gets transported to the Star Wars Rebels universe. He could team up with the Ghost crew. His advanced combat skills and Spartan armor would be a huge asset against the Empire. Maybe he'd share his knowledge of advanced weaponry with the rebels.
One idea could be that the Spartans from Halo are sent through a wormhole and end up in the Star Wars galaxy. They could then get involved in the Clone Wars, with their advanced technology and combat skills being a huge asset or a source of great confusion among the different factions. Maybe they team up with the Jedi at first, but then some misunderstandings occur due to their different ways of handling situations.
A great plot could be that Master Chief somehow gets transported to the Star Wars universe. He could find himself in the middle of a battle between the Sith and the Jedi. His combat skills and advanced armor would be a huge asset to either side. Or perhaps there could be a story where the Forerunners have some ancient connection to the Force in the Star Wars galaxy. This could lead to a search for lost Forerunner technology that could change the balance of power in the Star Wars universe.
Another idea is a story where the Covenant from Halo discovers the Force in the Star Wars universe. They might see it as a new form of 'holy' power and try to either harness it or destroy those who possess it. This could lead to some epic battles between the Covenant and the Jedi or Sith.
In 'halo 4 crossover fanfiction', a great crossover idea is with the Ghost in the Shell universe. The high - tech world of Ghost in the Shell combined with Halo's advanced military tech would be fascinating. You could also consider a crossover with the Metroid series, where the Spartans face off against the space - faring threats like Samus does. And a crossover with the Devil May Cry series would bring some stylish combat to the Halo universe.
A cool concept would be a hybrid character. Imagine a Spartan who has been genetically altered with some dragon DNA. This character could have the strength and combat skills of a Spartan along with the ability to breathe fire or fly like a dragon. Or perhaps the Covenant could be interested in the dragons in the HTTYD world because they see them as a new form of powerful weaponry to add to their arsenal.
Another concept could be a story where a character from Halo, say Master Chief, gets transported to the Overwatch universe. He has to adapt to the different rules and powers there while trying to find a way back home. Along the way, he could form unexpected alliances with Overwatch heroes and learn about their world, and they could learn from his military discipline and combat experience.
Maybe the Forerunner technology in Halo could be related to some of the pre - war technology in Fallout. A story could explore how the two different technological systems interact. For example, the power armor in Fallout could be enhanced with Forerunner tech, creating a new super - powered suit.
For 'halo anime crossover fanfiction', a cool concept is to mix the Covenant from Halo with the Titans in Attack on Titan. The Covenant's alien races and their zealotry could be an interesting contrast to the humans fighting Titans. Also, think about having Cortana, the AI from Halo, integrated into the world of Ghost in the Shell. Her digital existence could bring new perspectives to the cybernetic world of that anime.