Some fanfictions combine the two universes by having characters from both worlds meet in a neutral or new setting. For instance, a new island or city that is a melting pot of both Naruto - like ninjas and Black Lagoon - style mercenaries and criminals. Here, they interact, form alliances or rivalries, and the story unfolds with all the drama and action that comes from the clash of these two very different fictional cultures.
One way is through power systems. The biotics in Mass Effect and the chakra in Naruto can be related. Maybe a character in a fanfiction discovers that biotics are a form of chakra or vice versa. Also, the different races in Mass Effect and the clans in Naruto can interact in terms of politics and alliances. For instance, the Uchiha clan could form an alliance with the Salarians based on their shared intelligence and strategic thinking. And the stories can also use the different settings, like having a battle take place on a Mass Effect planet but with Naruto - style combat techniques.
In SCP Foundation crossover fanfictions, the combination usually starts with a premise that allows the two universes to interact. It could be something like a scientific experiment gone wrong that tears a hole between the SCP universe and, say, the 'Doctor Who' universe. Then, the characters from both sides start to encounter each other. The SCP Foundation might try to contain elements from the other universe as if they were new SCPs, while the other side might be trying to understand the strange and often dangerous SCP entities. Writers also play with the power levels. For instance, if it's a crossover with a superhero universe, they'll figure out how the SCP entities' powers compare to those of the superheroes. Sometimes, they'll create new hybrids of characters or entities by mixing the traits of both universes. For example, an SCP entity with the powers of a 'Superman' - like character from a crossover. This way, they make the story unique and full of unexpected twists.
Some fanfictions blend the two universes by introducing elements of one into the other. For instance, the Death Note's rules might be applied in the Naruto universe. So a character in Naruto might get hold of a Death Note - like object with similar powers, and then the story explores how that changes the Naruto world's balance of power and relationships. It can also involve characters from Death Note trying to understand the ninja way of life in Naruto, which is full of loyalty, honor, and complex clan politics.
Often through character crossovers. They put characters from both series in the same story. Like Harry and his friends could end up in Middle - earth, or the hobbits could find themselves at Hogwarts.
Well, one way could be through a crossover spell or some sort of interdimensional rift. Maybe a character from Twilight somehow ends up in the Naruto world and has to adapt to the ninja way of life.
Often, it combines them through crossovers. For example, a portal could open between the Naruto universe and Shinji's world, allowing characters to travel between them.
Some writers combine the two universes by setting the story in a new location that has elements of both shows. Let's say a new town is created that has a prison - like facility but also has the normal civilian life aspects from 'Just Friends'. Characters from both shows are then brought there and their interactions are written about. This allows for new and interesting dynamics to be explored as the characters from different backgrounds have to co - exist and deal with each other's quirks and personalities.
Often, they put the Harry Potter characters into the game world's setting. So, the Hogwarts castle might be re - created in a digital game environment. The characters then interact with the game's mechanics, like quests or leveling up, while still using their magical powers.
In many 'Master Chief RWBY' fanfics, they combine the universes by having Master Chief somehow end up in the RWBY world. This could be through a portal or some kind of interdimensional rift. Once he's there, his high - tech equipment and combat training from his own universe contrast with the more magical and combat - school - based RWBY world.
Some writers create a situation where the problems in the Supernatural world are related to Hermione's world. Maybe a dark wizard has escaped into the Supernatural universe and is causing chaos. Hermione then has to team up with the Supernatural characters to stop this threat. This allows for a seamless combination of the two universes, as they both have to work towards a common goal using their respective skills and knowledge.