Maybe there's a relative of Magnus' uncle who has some old - fashioned views and doesn't approve of Alec. This person could try to cause trouble between Alec and Magnus during the meeting. They might spread rumors or create awkward situations to drive a wedge between them. For instance, they could claim that Alec will bring danger to their family because of his Shadowhunter nature.
It could be another warlock who doesn't like the idea of Alec, a Shadowhunter, getting involved with Magnus and his family.
In the 'alec meets magnus uncle fanfiction', it could be that Magnus' uncle has some interesting stories about Magnus' past that he shares with Alec. This could help Alec understand Magnus better. For example, he could learn about Magnus' early days as a warlock and the challenges he faced. It might also be a situation where Alec's Shadowhunter background causes some initial tension, but then they find common ground through their love for Magnus.
It's also possible that the real antagonist is Alec's own insecurities. Magnus might be using Alec's insecurities to manipulate him. So in a way, Alec's internal struggles could be seen as the antagonist. But again, from the title's perspective, Magnus is the one directly involved in the act of manipulation.
One great Alec meets Magnus fanfiction is 'The Meeting of Hearts'. It beautifully portrays their first encounter with vivid descriptions. Another one could be 'Alec and Magnus: Destiny's Bond' which delves into how their relationship develops over time. There's also 'Unforeseen Encounters' that has an interesting take on their initial meeting from Magnus' perspective.
Well, AO3 is a great resource. It has a tagging system that allows you to easily search for Alec meets Magnus fanfiction. Tumblr can also be a source. Sometimes bloggers share links or even write their own short fanfictions about the two characters meeting. Additionally, some fan - run forums may have threads dedicated to sharing and discussing such fanfictions.
It could be a powerful warlock who has found a way to manipulate time and space. He wants to stop Paige and Prue from joining forces because he fears their combined power. So he creates various obstacles and illusions to keep them apart.
Maybe a powerful rogue ninja who has discovered a way to steal the powers of divine entities. He sets his sights on Amaterasu and Naruto because he knows that if he can combine their powers, he will be unstoppable. He creates various traps and illusions to separate them and weaken them so that he can carry out his evil plan.
A powerful new pirate group could be the main antagonist. They might be after the same treasure or territory as Luffy and Shanks. They could have some unique and dangerous abilities, like the ability to control sea monsters. Their leader could be a former crewmate of a well - known and feared pirate, who has his own vendetta against both Luffy and Shanks for some past reasons.
There could be an ancient force that is awakened by the meeting of Harry and Hela. This force wants to destroy both of them because their combined powers could potentially stop it from achieving its goal of spreading chaos and destruction throughout all the realms. It would use all kinds of devious means to try and separate them and defeat them one by one.
Maybe a powerful warlord from Negan's world who somehow follows him into Artemis' realm. This warlord, with his own thirst for power and destruction, would oppose both Negan (if he starts to side with Artemis) and Artemis herself, wanting to take over the new world he has found.
It could be another god who is jealous of Zeus' interest in Atreus. Maybe a god who feels that Atreus is an outsider and doesn't belong in their divine affairs.