One way could be through the concept of power. In Naruto, the Rinnegan gives extraordinary powers. In Game of Thrones, power is also a central theme. Maybe a character with the Rinnegan could be teleported into the Game of Thrones world and use their powers to vie for the Iron Throne. For example, they could use the Rinnegan's abilities to control minds, like the way the Red Woman in Game of Thrones uses her magic to influence people, but on a much larger scale.
One way could be through a magical portal. Imagine in a fanfic, a powerful mage in the Game of Thrones world accidentally opens a portal to the Naruto universe. Dark Naruto, with his edgy and powerful nature, could be seen as a threat similar to some of the dark forces in Game of Thrones. He might form an alliance with a power - hungry lord in Westeros, thinking he can use their resources to achieve his own goals in the Naruto world. For example, if he teams up with Littlefinger, they could plot to take over both kingdoms using Dark Naruto's powers and Littlefinger's cunning.
Well, it might involve the political intrigue. The complex politics in Game of Thrones could be combined with the NERV organization's secrecy in Evangelion. Maybe the different houses in Game of Thrones are vying for control over the Evangelion units. And the pilots of Evangelion could be seen as pawns in this political game, just like many characters in Game of Thrones are used by the powerful lords.
One way to merge them could be through character crossovers. For example, a character from Skyrim like the Dragonborn could find themselves in the world of Game of Thrones. They might use their unique abilities, such as Thu'um, to influence the power struggles in Westeros. Maybe they could form alliances with certain houses, or use their combat skills to fight in the battles there. Another aspect could be the introduction of Skyrim's magic system into the Game of Thrones universe. Spells like healing or firebolts could change the dynamics of warfare and politics in Westeros.
One way to merge the two universes could be through a magical portal. Imagine if the White Walkers from Game of Thrones somehow found a way into the world of Black Panther. The Wakandan technology and the magic in Game of Thrones would create a really interesting dynamic. The Wakandans with their advanced weapons and the ability to harness vibranium could potentially fight against the White Walkers. Their stealth technology might give them an edge in surprise attacks. And on the other hand, the magic users in Game of Thrones could be intrigued by the vibranium and its unique properties, perhaps trying to use it for their own purposes.
One way could be through a powerful magic - ninjutsu hybrid spell. Maybe a character with knowledge of both worlds accidentally creates a portal that merges the two. For example, if a shinobi in Naruto world somehow gets hold of a magic item from Highschool DxD and activates it in a wrong way.
One way they could collide is through a magical portal. Imagine Doctor Strange discovers a portal that leads to the world of Game of Thrones. The Avengers could then enter this new world. They might be shocked by the medieval setting and the presence of dragons. Thor, being from a somewhat similar mythical background, could potentially communicate with the dragons. This would lead to an interesting alliance between the Avengers and the dragon riders in Westeros, creating a unique fanfiction scenario.
The political intrigue aspect can also be combined. The power struggles in Game of Thrones are well - known. In a fanfic, these could be mirrored in the Elder Scrolls universe. For instance, the various houses vying for the Iron Throne could be compared to the different races and factions in Elder Scrolls fighting for control over a particular region or resource. A character from Elder Scrolls could be inserted into the Game of Thrones world to observe and perhaps influence the political machinations, or vice versa.
One way could be through a powerful jutsu or hogyoku - like device. Maybe Naruto discovers a strange object that has the power to warp realities, similar to the hogyoku in the Bleach universe where Aizen Sousuke is from. This object could start to merge the two worlds, bringing the ninja world of Naruto and the Soul Society of Bleach together. As a result, Naruto and his friends would encounter Soul Reapers, hollows, and other Bleach elements, while the Soul Reapers would have to deal with the unique powers and politics of the ninja world.
You could also have a character who has a connection to both universes. Maybe a half - Naruto - half - Angeloid being. This character would act as a bridge between the two worlds. They would introduce the concepts of one universe to the other. For example, they could teach the ninja in Naruto's world about the advanced machinery of the Angeloid universe and at the same time show the Angeloid the importance of things like honor and loyalty in the ninja world. As this character moves between the two universes, the two start to blend together more and more.
One way could be through magic. In the world of Harry Potter, Tom Riddle is a powerful wizard. In Game of Thrones, there is also magic, albeit different. Riddle could perhaps use his dark magic to cross over into the Game of Thrones universe. Maybe he'd be drawn to the power struggles there, similar to his quest for power in the wizarding world.