Maybe it's a group of rogue demigods who have turned to the dark side. They found a way to manipulate the power of ice and are using it to try and take over Camp Half - Blood. Their leader could be a demigod with ice - related powers who has gone mad with power.
One idea could be Percy having to journey into a frozen realm in the Underworld to retrieve a magical ice artifact that is key to saving Camp Half - Blood from a new threat. Maybe he teams up with a frost - giant who has a change of heart and helps him.
Well, in some fanfictions, Percy might control ice through a new power bestowed upon him by some mysterious god or entity. Maybe he discovers he has the ability during a quest when he's in a really cold and magical place.
In fanfiction, Percy Jackson being the 'God of Ice' is a creative and non - canonical interpretation. It could be a writer's unique take on the character, perhaps giving him ice - related powers and a new role within the fan - created narrative. It might involve him having control over ice, snow, and cold elements, different from his original abilities in the official Percy Jackson series.
There could be a fanfiction where a character with ice powers is actually an enemy in the Percy Jackson world. They are trying to freeze over all the water sources, which would be a huge threat to the demigods. Percy and his friends have to figure out how to stop this ice - powered foe. They might discover that the only way is to find a way to combine fire and water powers in a unique way, like using the heat from Hephaestus - forged weapons along with Percy's water control to melt the ice and defeat the enemy.
One scenario could be Percy sacrificing himself to save his friends from a powerful and ancient evil. Maybe he faces off against a primordial being and uses his powers to hold it back long enough for his friends to escape, but at the cost of his own life.
One of the sad moments could be when a character like Annabeth is in a situation where she feels completely alone and betrayed. In some fanfictions, she might be separated from Percy in a cruel way, like being trapped in a different dimension where she can't reach out to him. This not only makes her character suffer but also tugs at the readers' heartstrings as their relationship is so central to the series.
There's also 'Ice Skating in Camp Half - Blood'. This one is set in the Camp Half - Blood and features the characters trying to incorporate ice skating into their training. It's a fun read as it shows how the demigods with their different powers and personalities adapt to this new form of activity.
A powerful ice giant could be the antagonist. This ice giant could have a grudge against Percy for some past encounter and uses its ice - magic to freeze him. It wants to keep Percy out of the way while it tries to invade Camp Half - Blood or other places important to the demigods.
Another good place is Archive of Our Own (AO3). There are many creative writers who post their Percy Jackson ice fanfictions there. The tagging system on AO3 makes it easy to filter out the stories you're interested in. You can look for tags like 'ice', 'Percy Jackson', and related keywords to find the fanfictions you want.