One common theme is redemption. Since Luke has made some bad choices in the original lore, many fanfictions focus on him trying to make up for his mistakes.
One great Harry Potter Luke Castellan fanfiction is 'The Path of Luke Castellan' on FanFiction.net. It delves deep into his backstory and his relationship with the world of Harry Potter in a really interesting way.
Luke's magic from Greek mythology might be more elemental and based on the power of the gods. Harry's magic in the wizarding world is more about spells and potions. When they interact, Luke might be able to do things like control the weather in a way that amazes Harry. Harry, on the other hand, could use his spell - casting to create objects or illusions that Luke has never seen. Their different backgrounds could lead to a lot of learning and mutual admiration.
One plot idea could be that Harry Potter and Luke Castellan somehow meet in a magical realm outside of their own stories. Maybe they are brought together by a powerful magic that needs their combined powers to defeat an ancient evil. Another idea is that Luke, with his knowledge of Greek mythology, helps Harry understand some of the more mysterious aspects of magic in the wizarding world that have roots in ancient myths.
One common theme is redemption. Since Luke had some dark actions in the original story, many fanfictions explore his journey to make up for what he's done.
Luke Castellan once fell in love with a girl from the same camp. They met during a training session. He was instantly attracted to her bravery. They started to secretly meet in the forest, sharing their dreams and fears. But as Luke's path started to turn darker, their love was put to the test. Eventually, she couldn't follow him into his wrongdoings and they had to part ways.
In many fanfictions, Percy's powers might be explored in new ways in relation to Luke. For example, how his control over water could be used to counter Luke's actions. Luke may be given different abilities or backstories that make him more of a three - dimensional character. He could be shown as having been influenced by external forces that made him turn bad, rather than just being a 'born villain' as some might view him in the original. This changes how the two characters interact and how the story unfolds.
In fanfiction, the relationship between Percy Jackson and Luke Castellan can be complex. Often, it shows a dynamic of rivalry. Luke is initially a somewhat of a mentor figure to Percy, but then his true motives are revealed which sets them at odds. Percy, being the hero, is constantly in a struggle against Luke's devious plans.
Another great one is 'Luke's Hidden Strengths in Fanfiction'. This story focuses on uncovering the hidden strengths within Luke that were perhaps not fully explored in the original work. It gives him more depth and makes for a very engaging read.