In some fanfictions, Uthur might be on the verge of starting a war that Camelot cannot win. His pride and stubbornness won't let him back down. Merlin and Arthur, who both love Camelot deeply, see no other option but to kill Uthur to prevent the war. They know it will be a huge sacrifice but believe it's for the greater good of the kingdom.
On the other hand, it could also bring them closer in a way. They now share a very dark and heavy secret. This shared burden might make them more reliant on each other, and they would have to support one another through the emotional turmoil that follows. Merlin would be there for Arthur as he grapples with his feelings, and Arthur would start to understand Merlin's complex role in Camelot even more.
A possible plotline could be that they discover their brotherhood later in life. Maybe there was some mystery or secret that kept it hidden. This revelation could change the course of Camelot's future as they reevaluate their relationship and roles. Another plotline could involve them facing a common enemy that only their combined strength as brothers can defeat.
One possible plotline could be that Naruto discovers Danzo's dark secrets and decides he has to take action. Maybe Danzo was planning something truly evil against the village that Naruto couldn't let stand. So Naruto, with his newfound power and determination, confronts Danzo in a battle. Naruto uses his Rasengan and outsmarts Danzo's Sharingan - based jutsu to finally defeat him.
One possible plotline could be that Naruto is forced into a situation where he has to kill Itachi to protect the Hidden Leaf. Maybe Itachi is being controlled by some dark force and Naruto, with great reluctance, has to end his life to save the village and his friends.
One possible secret could be that Merlin is a powerful sorcerer from an ancient and powerful magical lineage. Maybe his family has a long - standing connection to Camelot that has been kept hidden.
One possible plotline could be that Harry is somehow transformed into a killing machine against his will. Maybe he's under a dark spell or some sort of mind control. And he has to fight against this new - found, violent nature while also dealing with his friends who are trying to save him.
Another plotline could be a time - travel scenario. Draco gets sent back in time to Camelot. He becomes an apprentice or a follower of Arthur Pendragon. He then has to learn the ways of Arthur's court, deal with the politics and magic there, and in the process, he grows as a person, bringing back some of Arthur's wisdom to his own time when he eventually returns.
One possible plotline could be that Naruto, in his 'godlike' state, is pushed to the brink by Sasuke's actions which threaten the safety of the village. Naruto might see no other option but to end Sasuke's life to protect everyone he loves. For example, if Sasuke were to ally with a powerful and evil force that was bent on destroying Konoha, Naruto's extreme power could be the only thing to stop him.
One possible plotline could be Percy gathering a powerful group of demigods and allies. They might embark on a quest to find the ultimate weapon that can defeat Gaea. Along the way, Percy could face many internal struggles, like doubts about his own abilities. He might also have to make some tough choices that could endanger his friends but are necessary to defeat Gaea.
One possible plotline could be that Snape discovers a hidden weakness of Voldemort. Maybe through his years of spying, he finds out that a certain spell, when combined with an ancient magic artifact, can destroy Voldemort. So he devises a plan to get hold of the artifact and uses the spell at a crucial moment when Voldemort is off - guard, perhaps during a major battle when Voldemort is focused on other opponents.