There might be a secret organization that has been hunting down any descendants of Lilith for centuries. When they discover Naruto's identity, they become his main antagonists. They could have ancient motives and dark magic at their disposal, making them a formidable foe for Naruto as he tries to understand and control his powers as the son of Lilith.
It could be those who fear Naruto's power as the son of Lilith. For example, some of the more traditional ninja clans might see him as a threat to their power and status in the ninja world.
The main antagonists could be those who were once enemies of Obito. They might see Naruto as a threat simply because of his relation to Obito. For example, some of the old - school ninja clans who still hold grudges against Obito's actions in the past could target Naruto.
Maybe there could be an Asgardian traitor who doesn't like the idea of a half - human being part of the royal family. This traitor could team up with some of Naruto's enemies from the ninja world to create chaos. They could plot to steal Naruto's powers or his special weapon if he has one, and Naruto has to stop them to protect both Asgard and the ninja world.
It could be the people in the village who are against Naruto because of his new identity as the son of Manda. They might see him as a threat to the village's stability.
The main antagonists could be the Akatsuki from the Naruto world. They might see Naruto's new powers as a result of being Sparda's son as a great asset and try to capture him to use for their own evil plans, like creating some sort of super - weapon or using his power to take over the ninja world.
Well, perhaps there could be a powerful underwater clan that sees Naruto as an abomination because he is a half - human, half - Neptune's son. They view his existence as a threat to the balance of the ocean realm and the ninja world. They send their best warriors to stop Naruto from growing in power and spreading his influence. Also, a mad scientist - type character who wants to experiment on Naruto to unlock the secrets of his Neptune - heritage could be an antagonist.
Well, it could be about Naruto having some unique powers inherited from Lilith. Maybe he has some dark magic abilities that he has to learn to control. And he might face challenges from the ninja world because of these strange powers.
In this fanfic, Lilith could be an original character created by the author. She might be a powerful and mysterious figure with special abilities that make her suitable to train Naruto.
Obviously, Naruto would be the main character. Since it's about him being the son of Lilith. And Sasuke could also be an important character as he is Naruto's rival and friend. Their relationship might be affected by Naruto's new identity.
One possible main antagonist could be a rogue ninja who was once an apprentice of Orochimaru and is jealous of Naruto's connection to the Sannin. This ninja might want to steal Naruto's new - found powers related to the Sannin. Another could be a hidden organization that sees Naruto as a threat because of his potential with the Sannin's abilities. They fear he will disrupt their plans for power in the ninja world.
One possible antagonist could be a jealous Roman god who doesn't want Naruto, as the son of Jupiter, to gain too much power. Maybe Pluto, who might see Naruto as a threat to his own domain in the afterlife.