Severus Snape could also be an interesting choice. His double - agent nature in the Harry Potter series could translate well into the Assassin's Creed world. He could be a spy within the Templars or use his potions knowledge to create new substances for the Assassins, like a potion that enhances stealth or a poison for their blades.
Harry Potter and Altair would be a great combination. Harry's sense of justice and Altair's Assassin skills would make for an exciting duo. They could learn from each other, with Altair teaching Harry about stealth and combat techniques from the Assassin's Creed world, and Harry showing Altair the power of magic.
I think Sasuke would be really interesting. He has that brooding and powerful nature. In the Assassin's Creed world, he could be a very effective assassin. His Sharingan would give him an edge in combat and his ability to quickly analyze situations would be useful for assassinations. He could also learn from the assassins' techniques and incorporate them into his own fighting style.
I think Naruto would be the most interesting. His energetic and determined personality would make for great stories in the Assassin's Creed world. He'd be constantly trying to adapt and use his ninja skills in new ways. His ability to make friends and inspire others would also lead to some interesting interactions with the assassins.
I think Sasuke would be quite interesting. His dark past and thirst for power could be paralleled with some of the Assassin's Creed characters' motives. He could learn new ways to use his skills in the Assassin's Creed world and maybe even find a new purpose.
I think Michael Corvin could be an interesting crossover character. He's a hybrid in the Underworld series, which means he has a unique set of abilities. In the Harry Potter world, he could be seen as a strange new kind of magical being. He might be able to help the wizards understand different types of magic that are more physical and instinct - based like his own. Also, his journey of self - discovery in the Underworld could be paralleled in the wizarding world as he tries to find his place among the wizards and witches.
I think Naruto and Altair would make an interesting pair. Naruto is all about exuberance and his belief in the power of friendship and hard work. Altair, on the other hand, is a more stoic and methodical Assassin. Their different personalities would create great character dynamics. Naruto could learn about Altair's strict code of conduct and Altair could be intrigued by Naruto's ability to keep going no matter how tough the situation is.
Dumbledore would be an amazing crossover. His wisdom and power are so great. In Storybrooke, he could act as a sort of guiding figure for the characters. He could help them understand the deeper magic at work in their town, and maybe even teach some of them about the more noble aspects of magic, which could be different from what they already know in their fairy - tale world.
Severus Snape could also be a great crossover. His sardonic nature and his skills in potions could translate well in Bioshock. He might be interested in the way ADAM is created and used. He could also use his Occlumency skills to hide from the more dangerous inhabitants of Rapture. His complex character would add a lot of depth to the story, as he could be a reluctant ally to Harry in this strange new world or have his own hidden motives for being there.
Hermione. She's intelligent and resourceful. In the Tangled world, she could use her knowledge of spells and potions to solve problems. For example, she could brew a potion to make Rapunzel's hair grow even longer and stronger if it was damaged in some way.
Arya Stark would be really interesting. She already has assassin - like skills in the original GoT. In a crossover, she could learn more advanced techniques from the Assassins' Creed world and become an even more formidable force.