The energy shields in Halo could be combined with the natural defenses of Pandora. For example, the Na'vi could use the technology to create shielded areas around their sacred places. Also, the UNSC's weaponry could be enhanced with the unique materials found on Pandora. The super - strong metals there could make Halo weapons even more durable.
One way is through biotics. In Mass Effect, biotics are a form of biological manipulation of mass effect fields. Cthulhu Mythos entities often have strange, otherworldly biological features. Fanfiction could combine these by having a character gain new biotic abilities inspired by Cthulhu Mythos creatures. For example, instead of the normal biotic powers like lift and throw, a character might develop the ability to summon dark tentacles similar to those of a Cthulhu - like being.
In a fanfiction, the two universes' technologies could combine in terms of communication. The US soldier could introduce more advanced radio or communication devices. These could be used to better coordinate the huntsmen and huntresses in RWBY. Also, the soldier's knowledge of military engineering could be used to build stronger fortifications in RWBY settlements. This would help in defending against Grimm attacks. The soldier could also work on improving the airship technology in RWBY using some of the engineering concepts from the US military.
The sleek, high - tech look of Halo's UNSC and Covenant ships can contrast sharply with the gothic, ornate designs of Warhammer's spacecraft and architecture. In fanfiction, authors might describe how the angular, metallic forms of Halo coexist with the spiky, daemon - influenced aesthetics of Warhammer. For example, a UNSC base on a Warhammer world might look like a strange outlier, or perhaps over time, it starts to adopt some of the local, more flamboyant design elements.
In a crossover, the Dragonborn's ability to absorb dragon souls could be related to the Halo universe in an interesting way. Maybe the dragon souls contain some sort of energy that can be used to power up Halo technology. The Dragonborn could team up with Halo scientists to study this. And the Spartans' training in various terrains could be combined with the knowledge of Skyrim's different regions. They could teach the Skyrim locals about new combat strategies, and in return, learn about the magic and lore of Skyrim.
Well, one way is to have the magic from Harry Potter interact with the physical threats of the Tremors universe. For instance, the protective spells around Hogwarts could be modified to keep out the Tremors creatures. Or the Portkeys could be used to transport characters to areas affected by Tremors.
Another aspect could be the fusion of their worlds' elements. In Mortal Kombat, there are dark and hellish realms, while Naruto has its own unique elemental chakra system. A fanfiction could explore what would happen if the dark magic from Mortal Kombat's realms seeped into the Naruto universe and affected the chakra. Maybe it could create new types of jutsu or even corrupt some of the ninja. It would be a great source of conflict and adventure in the story.
Maybe a character from the Naruto universe, like Naruto himself, could be summoned to Wakanda due to some powerful magic or technology gone wrong. He would bring his ninja skills and values, and his presence could disrupt the power balance in Wakanda. This would lead to various interesting scenarios, such as Naruto learning about Wakandan culture and the Wakandans learning about ninja techniques.
One way to combine them could be through a crossover device. For example, a powerful Pokemon like Mewtwo could accidentally open a portal to the Avengers' universe. Then, the Avengers might mistake the Pokemon for some kind of new alien threat. They would try to contain it, but soon realize that the Pokemon has no malicious intent. Meanwhile, the Pokemon trainer who follows Mewtwo through the portal has to team up with the Avengers to find a way back home and also deal with any villains in the Avengers' world that might try to use the Pokemon for their own gain.
Well, it could be that the magic from Harry Potter's world and Android 18's advanced technology somehow interact. Maybe the spells in Harry Potter are used to enhance or modify Android 18's abilities. For example, a spell could be cast on her to make her energy blasts more powerful or her speed even faster.
If we think about it, the Sharingan in the Naruto universe has some similarities to the power of the Death Note in terms of perception. So, a character like Sasuke could potentially use his Sharingan to better understand the workings of the Death Note. He could then teach Naruto how to use it in a more strategic way. Also, the teleportation jutsu in Naruto could be used to quickly get to the location of the target whose name is about to be written in the Death Note, making the process more efficient.