The obvious antagonists would be the Death Eaters. They are Voldemort's followers and are often causing trouble in the wizarding world. In this fanfiction, they might be the ones who have put Cedric in danger, either to lure Harry or for some other dark purpose.
The fanfiction could show that Harry discovers a secret passage that leads to where Cedric is held captive. He has to face various magical traps and challenges on the way. Once he reaches Cedric, he uses his Gryffindor courage and his knowledge of magic, like the Shield Charm to protect Cedric from incoming spells, and then they escape together, with Harry being the hero who saves Cedric.
In many fanfictions where Hermione saves Cedric, it often involves her using her intelligence. Maybe she discovers a plot against Cedric in time and uses her magic skills to prevent his death. For example, she could use a powerful protection spell or figure out a way to expose the real danger that was set for Cedric in the Triwizard Tournament.
There's a fanfiction called 'Cedric's Unfinished Story'. In this one, it explores what could have happened if Cedric had survived the Triwizard Tournament. It's really interesting as it weaves new adventures for Cedric, involving him in the fight against Voldemort in a different way.
Another theme is heroism. Harry is portrayed as a hero, which is in line with his character throughout the series. But in these fanfics, it's more focused on this one specific heroic act and how it changes things. For example, in some fanfics, it changes the way the wizarding community views Harry, as he's not just the Boy Who Lived but also a savior in a different sense. Also, there's often the theme of defying fate. Cedric was meant to die in the original story, but in these fanfics, Harry's actions change that pre - determined fate, which adds an interesting layer to the story.
Another good one is 'Cedric's Salvation by Harry'. In this fanfic, not only does Harry save Cedric from immediate death, but he also has to deal with the after - effects. It's a long - form fanfic that explores the consequences of that rescue on the wizarding world and on their own relationship, which is really interesting.
One great 'Harry Potter and Cedric Diggory' fanfiction is 'The Cedric Diggory Chronicles'. It delves deep into Cedric's life before the Triwizard Tournament. It shows his relationships with his friends and family, and how he prepared for the challenges at Hogwarts. It gives a more in - depth look at his character, making him more than just a tragic figure in the original story.
One common theme is redemption. Fanfiction often gives Cedric a chance to redeem himself or to show his true heroism in different situations. Another theme is friendship, exploring his relationships with Harry and other characters in more depth.
A popular author in the Cedric Diggory fanfiction world is GinnyWriter23. Their fanfictions often have a lot of emotional depth when it comes to Cedric. They explore his relationships with other characters in a very nuanced way. Also, RemusLupinFan has written some great Cedric - centric stories that are not only well - written but also manage to stay true to the spirit of the Harry Potter universe while adding new elements to Cedric's character.
One popular aspect in such fanfiction could be the exploration of their different personalities. Cedric, being the charming and popular Hufflepuff, and Harry, the brave Gryffindor hero. Writers might create scenarios where they first become friends and then gradually develop deeper feelings. For example, they could be paired up for a special project at Hogwarts which makes them spend a lot of time together and realize their mutual attraction.