Mard Geer is a very interesting character to focus on. His complex relationship with Zeref and his extreme loyalty to Tartaros provide a lot of material for exploration. You could also write about Gray Fullbuster. His struggle with his dark side and his connection to the demons of Tartaros make him a great focal point. Another option is Erza Scarlet. Her strength and determination in the face of the Tartaros threat can lead to some exciting storylines.
I think Natsu Dragneel can be an interesting character to focus on in a Tartaros Arc fanfiction. His search for Igneel and how that intersects with the events of the arc can create a lot of drama. Additionally, the Tartaros members' reactions to Natsu's dragon - slayer magic could be explored. Then there's Lucy Heartfilia. Her celestial spirit magic could be used in unique ways against Tartaros, and her character development during the arc can be further expanded in a fanfiction.
For a Fairy Tail Tartaros Arc fanfiction, you might consider writing about a new magic that is introduced during the arc. It could be a magic that is a combination of different existing magics in the Fairy Tail universe. The story could revolve around a young wizard who discovers this new magic and uses it to turn the tide in the battle against Tartaros. You could also explore how the discovery of this new magic affects the power dynamics within the guild and among the other characters in the arc.
The adaptation is quite good. It captures the key elements and action scenes effectively.
Natsu is always an interesting character to focus on. His determination and his unique fire - based magic can lead to some exciting adventures on Tenrou Island. He could be on a quest to find a powerful fire - related relic hidden on the island. Another great character is Lucy. Her celestial spirit magic can add a different dimension to the story. She might use her spirits to help her and her friends navigate the dangerous parts of Tenrou Island or solve mysteries there.
In the Tartaros Arc, a major plot point is the threat of the dark guild Tartaros and their evil plans. There are epic showdowns, like Natsu vs. E.N.D., and emotional moments as characters confront their pasts and sacrifices are made.
Lucy is another popular choice. In the Edolas arc, her intelligence and determination can shine through. Maybe she's the one who figures out how to navigate the strange new world and its magic, and her relationships with the Edolas versions of the characters can be explored in interesting ways.
Erza is extremely popular. Her strong - willed and powerful nature means there are countless stories that can be told about her. Maybe she has to face an opponent who can nullify her magic, and she has to find a new way to fight. Juvia is also a fan - favorite. Stories about her unrequited love for Gray and her growth as a mage are always interesting. And of course, Happy, Natsu's sidekick, can add a lot of humor to any fanfiction.
Mavis is definitely a popular choice. Her unique powers and her role in founding the guild make her a central figure. Zeref is also often focused on, given his connection to Mavis and his powerful and mysterious nature. Then there's Precht, as he was an important part of the early guild and his actions had a significant impact on the future of 'Fairy Tail'.
One possible aspect of a Fairy Tail Natsu and Tartaros fanfiction could be Natsu's battle against the powerful foes in Tartaros. He might face new and terrifying enemies that test his limits. His dragon slayer magic would be put to the extreme, and perhaps he discovers new powers along the way.
Erza is often a popular character to focus on. Her strong will and past connection to the Tower of Heaven make her a central figure. Fans like to explore her growth during the events of the tower, as well as her emotional turmoil regarding Jellal. Another popular character is Jellal himself. His complex character, being both a villain and a victim in the Tower of Heaven arc, offers a lot of room for exploration in fanfiction. Gray is also a favorite. His cool - headedness during the battles in the tower and his relationship with his friends, especially Natsu, can be further developed in fan - created stories.
One great 'Fairy Tail Tartaros' fanfiction is 'Tartaros' Redemption'. It focuses on a Tartaros member who starts to question their evil ways after interacting with Fairy Tail members. It has some really interesting character development and a unique take on the relationship between the two groups.