Maybe an OC that is an artificial being created by a powerful wizard long ago. The OC wakes up in the present day of the Danmachi world and has to learn about the new society and dungeon while also dealing with the fact that they are different from everyone else. They could form unique relationships with the existing characters as they try to find their place.
An OC who is a cursed adventurer. Every time they use their special ability, they lose a part of their memory. They join a familia to not only become stronger but also to find a way to break the curse. This would create a lot of drama and interesting interactions with other familia members as they struggle with their condition.
A plot could revolve around a magic item that is found in the dungeon. This item has the power to grant a wish, but only one. The harem members all have different desires, which causes a lot of tension. Some might want to use it for Bell's benefit, while others have more self - centered wishes. This would lead to a complex web of emotions and decisions within the harem.
One idea could be that the reincarnated character has knowledge of future events in the Danmachi world. For example, they know about certain monsters' weaknesses or hidden treasures. This could give them an edge as they navigate the dungeon. Another could be that they are reincarnated as a non - human race in the Danmachi world, like a spirit or a dwarf, and they have to deal with the different cultural and physical aspects of that race. A third idea is that the character reincarnates with a special ability that doesn't exist in the normal Danmachi world, like the power to control time on a small scale, which would completely change their adventures in the dungeon.
A plot for Gilgamesh Danmachi fanfiction might be that Gilgamesh discovers a hidden part of the dungeon that has a connection to his past. Maybe it contains ancient artifacts or secrets related to his origin. As he delves deeper, he has to team up with some of the local adventurers from Danmachi. They are initially skeptical of him but soon realize his power and knowledge are invaluable. Together, they face various challenges and traps, and Gilgamesh also has to deal with his own internal struggles as memories from his past start to resurface.
One idea could be to create an original character (OC) who has a unique power that catches the attention of a goddess. For example, an OC with the ability to manipulate time on a small scale. The story could revolve around how this power affects the relationship between the OC and the goddess, and how they team up to face challenges in the danmachi world. Maybe they have to deal with a powerful monster that is immune to normal attacks, but the OC's time - manipulation power gives them an edge in battle.
Another aspect is the world - building. In 'danmachi oc god fanfiction', the author might expand on the existing world of DanMachi. They could introduce new areas of the dungeon that are only accessible through the OC's special relationship with the god. This can add a whole new layer of mystery and adventure to the story.
A really cool concept for a 'naruto x danmachi fanfiction' could be that the tailed beasts exist in the Danmachi world but are sealed away in the deepest parts of the dungeons. Naruto has to team up with Bell Cranel and other adventurers to either free or reseal them. Along the way, Naruto shows them his ninja techniques and they in turn teach him about the magic and skills specific to the Danmachi world. This would create a great dynamic between the two different universes and their respective powers.
One idea could be that Naruto characters end up in the world of Danmachi. For example, Naruto himself could be mistaken for a new type of adventurer with his unique skills like shadow clones. His clones could be used to explore dungeons more efficiently, confusing the locals. Another idea is that Sasuke, with his Sharingan, might be able to quickly analyze the monsters in the Danmachi dungeons, giving him an edge in combat. And Sakura could use her medical ninjutsu to heal the injured adventurers in the world of Danmachi, which would make her a highly sought - after healer.
One idea could be exploring the origin of the OC in the covenant world. Maybe they have a special power that sets them apart from the regular covenant members.
One idea could be an OC who is a new Wolfblood in a pack and has to prove themselves. Maybe they have a unique power that the others don't have and they have to learn how to control it while fitting into the pack's hierarchy.
One idea could be an OC who is a long - lost relative of one of the main characters. They suddenly show up and cause a stir in the power dynamics. For example, if they are related to the main heir, they might have a claim to the inheritance as well, leading to all kinds of family drama and power struggles.