Maybe there's a powerful, ancient monster that Percy battles single - handedly to keep Artemis safe. The monster could be something like a Titan that has been awakened and is far too strong for Percy to defeat alone.
For the other characters, Percy's death could change the entire dynamic. His leadership and strength were often relied upon. Without him, there could be a power vacuum. Some might lose hope, thinking that if Percy couldn't survive, what chance do they have? Others might use his sacrifice as a rallying point, to become stronger and more united in the face of danger. But overall, it would be a very dark and difficult time for all those who knew and cared about Percy.
In this fanfiction, it could be that Artemis is in a situation where she is about to be killed or lose her powers forever. Percy, being the selfless hero he is, takes on a deadly task to prevent that from happening. Maybe it involves facing an ancient and malevolent god who has a vendetta against Artemis, and Percy uses his unique abilities and the element of surprise to try and stop this god, but at the cost of his own life.
Perhaps a powerful and corrupted demigod could be the main antagonist. This demigod might be jealous of Artemis' power and popularity among the other demigods. He devises a plan to harm her, and Percy, being loyal to Artemis, has to give his life to save her from this rogue demigod.
One possible plotline could be that Percy sacrifices himself to save Artemis from a powerful and ancient enemy. Maybe there's a prophecy that foretells his death in order to protect her. Another could be that Percy is tricked into a situation where he has to give his life for Artemis to prevent a great disaster from befalling the world of the gods. And perhaps in his death, he becomes a symbol of heroism that changes the way the gods view demigods.
It could be a powerful Titan who has escaped from Tartarus and blames Artemis for something in the past. So he's out to get her, and Percy has to stop him at all costs, even if it means his death.
Well, for starters, Artemis would probably be in shock. She's a goddess, not used to being saved in such a drastic way. She might become more protective of the demigods as a result. As for Percy's friends, they'd be angry too. Angry at the situation that led to his death. They might question why Percy had to be the one to sacrifice himself. And the younger demigods would look at Percy's death as a very solemn event, a reminder of the risks they all face. It would be a very dark time in the demigod community.
Percy's death would shatter the world of those who knew him. His friends like Tyson would be inconsolable. Tyson always saw Percy as a hero and a brother. The Hunters of Artemis might also be affected. They would respect Percy's sacrifice but also feel a sense of responsibility for his death. And the gods, who had often used Percy for their own ends, might start to question their actions. Some might feel remorse, while others might fear the chaos that could follow in the wake of Percy's death, as he was often a stabilising force in the often - tumultuous world of demigods and gods.
A possible plot twist in a 'Percy Dies Saving Artemis' fanfic could be that his death was not in vain, but rather a strategic move by some greater power. Maybe the Fates had planned it so that his death would create a distraction for an even greater evil that was about to be unleashed. Artemis, in her grief, could then discover this truth and be the one to take on this new threat with a new - found determination. Additionally, Percy's death could cause a shift in the balance of power among the demigods. With Percy gone, other demigods might step up in unexpected ways, and this could also play into the overall story as Artemis tries to navigate the new power dynamics in the demigod world.