Arwen could be a main character as well. Her beauty and grace, along with her connection to Aragorn, could make her an interesting foil to Vlad. She might be able to see the good in him, if there is any, or she could be a target for Vlad's more sinister intentions. Also, Sauron himself could be a main character in the sense that his plans would be affected by Vlad's presence in Middle - earth.
Gandalf would also be a crucial character. His wisdom and magic could either be a threat or an asset to Vlad. If Vlad is seen as a potential danger, Gandalf would try to keep him in check. But if Vlad decides to side with the good, Gandalf could use his knowledge to help Vlad better understand Middle - earth and its ways. Another main character could be Legolas. His archery skills and elven grace would add an interesting dynamic to the group, especially when dealing with Vlad's otherworldly powers.
Another interesting concept is that Vlad is a lost hero from a far - off land who arrives in Middle - earth. He could use his skills in combat and his knowledge of dark magic to help the Fellowship. For example, he might be able to use his vampiric speed to quickly scout areas or use his charm abilities to deceive the enemy. He could also have a complex relationship with Aragorn, either as a rival or an unexpected ally.
Alice from Wonderland. Her strange adventures in Wonderland could give her a unique perspective in Middle - earth. She might not be afraid of the strange creatures in Middle - earth as she has already faced the oddities in Wonderland. Maybe she could even make the trolls and orcs less menacing with her innocent charm.
One way it could work is by having Naruto characters in Middle - earth. For example, Naruto with his shadow clone jutsu could be a great asset in the battles against Sauron's forces. He could create clones to confuse the orcs and trolls. Meanwhile, characters from 'Lord of the Rings' could learn from Naruto's ninja skills. Frodo might pick up some stealth techniques from Naruto's training.
Aragorn could be a great choice. He already has a heroic and noble presence. In a harem fanfiction, he could attract various female characters from different regions of Middle - earth. His skills as a warrior and leader would make him an appealing focus for a harem story.
One idea could be a vampire character who is drawn to the power of the One Ring. Maybe this vampire, being a creature of the night and often associated with darkness and power -hunger, sees the ring as a means to gain ultimate power in Middle - earth. For characters, you could have a half - vampire, half - elf who struggles with their dual nature while being caught in the events related to the ring.
There could be a young hobbit with a brave heart and a thirst for adventure. Maybe an elf with a mysterious past and great archery skills.
Robin could be a thief - like character. He could steal important items from the enemy, just like Bilbo stole the One Ring from Gollum. His small size and agility would make him good at sneaking around, and he could provide valuable information to the Fellowship by eavesdropping on the enemy's conversations.
One possible plot could be that Eragon somehow gets transported to Middle - earth. He could meet Aragorn and learn from his leadership skills. Maybe they would join forces to fight a common enemy like a new breed of dark creatures created by a combination of Sauron's magic and the dark forces from Eragon's world.
In this crossover fanfiction, Dracula might be a lord in Middle - earth. He rules over a land that is feared by all, but he is intrigued by the power of the One Ring. He sends his minions to find it, but they cross paths with Frodo and his companions. This leads to a series of battles and negotiations. Dracula could be tempted by the power of the Ring, but also realizes that it could bring about his own downfall if he were to claim it.
In fanfiction, Hermione could find herself in a situation where she has to deal with the One Ring. Given her strong will, she might be able to resist its power for a longer time than most. However, she would also be aware of the danger it poses and try to find a way to destroy it, perhaps using a combination of her magic and the knowledge of the lore in Middle - earth.