One idea could be a fanfiction where Loki uses his magic to cover up his own dark circles. Maybe he's been up all night plotting against Thor and is trying to look his best in front of the other Asgardians. He could accidentally create a spell that gives everyone in the palace dark circles instead.
A plot twist could be that Loki's dark circles are actually a sign of a hidden power. In the fanfiction, as Loki discovers this, he has to learn to control this new aspect of himself. It could be that the darker the circles, the more powerful he becomes, but he also risks losing his sanity if he doesn't master it.
Dark Loki Fanfiction can be appealing because it often delves deeper into the psychological aspects of Loki. We get to see his inner turmoil, his possible descent into darker paths. It can also create more intense and complex relationships with other characters. For instance, his interactions with Thor or other Asgardians might be completely different in a 'dark' scenario, which makes for a very interesting read.
Power dynamics is also a common theme. Loki has his powerful and often dark magic, and Jane is just a mortal. How they interact in terms of power, with Loki being so much more powerful yet being affected by Jane in some way, is something that many 'dark loki and jane fanfiction' explore. For example, Loki may use his power to protect Jane in his own dark way, or his power may accidentally harm her, leading to conflict and growth in their relationship.
Another theme is redemption. Loki has his own history of being a villain, and in these fanfictions, his relationship with Tony can sometimes be a path towards redemption. Tony, on the other hand, might also find a new side of himself through this relationship. There are also themes of secrecy and betrayal as they both have their own motives and secrets that can come to the surface in their interactions.
Definitely Thor. Their complex relationship always adds depth to any story. You can explore their brotherly bond, rivalry, and how it changes in the context of 'The Dark World'.
One idea could be Loki having to team up with an unexpected ally from Asgard's underworld to stop a new threat that emerged during the events of 'The Dark World'.
The relationship between Loki and Thor is also frequently explored. In the Dark World, there's a lot of tension and history between them. Fanfictions might show them reconciling, or further straining their relationship, and how this affects the overall story of the Dark World.
Sure. One great Loki Dark World fanfiction is 'Loki's Redemption in the Dark World'. It delves into Loki's internal struggle during the events of The Dark World, exploring his complex relationship with Thor and his own motives in a really interesting way.
You can try fanfiction websites like Archive of Our Own (AO3). There are a vast number of fanfictions there, and you can use the search function to specifically look for 'Dark Loki' fanfictions. Another option is Fanfiction.net, which also has a large collection of works. Just make sure to read the tags and summaries carefully to find the ones that suit your taste.