Maybe Tony notices some unusual behavior in Loki. For example, Loki might be acting against his normal self - not as cunning or devious as he usually is. His actions could seem more robotic or forced, which makes Tony suspect that he's being controlled.
Tony might try to help Loki break free from the control. This could lead to a new alliance between them, which would be quite different from their usual relationship. They could then team up against the force that is controlling Loki.
In the fanfiction, Loki may have developed a sense of respect or even friendship for Tony. They are both very intelligent characters. Loki might admire Tony's ingenuity and courage. So when he realizes that Tony is in danger in Siberia, his new - found feelings for Tony drive him to save his life. Also, Loki might be bored with his usual villainous ways and wants to do something good for a change, and saving Tony seems like a good start.
One possible plotline could be Loki using Percy for his own mischievous ends. Maybe Loki wants to cause chaos in Percy's world, so he takes control of Percy and makes him do things that disrupt the normal order, like causing trouble at Camp Half - Blood.
Well, one possible plot could be that Thanos uses his mind - controlling powers on Loki to make him steal powerful artifacts for his collection. Loki, being under Thanos' control, has to go against his own nature at times. For example, he might have to target Asgardian relics that he would otherwise protect.
At first, it would be rocky. Loki is used to being a trickster and Tony is a bit of a control freak. But over time, they'd start to respect each other. Loki would see Tony's intelligence and resourcefulness, and Tony would see Loki's power and potential for good. Eventually, they'd become like family, looking out for each other.
In fanfiction, Tony Stark and Loki often make for an interesting pairing. Their personalities are quite different. Tony is a genius inventor, a bit of a playboy, and very human in his flaws. Loki, on the other hand, is a complex Asgardian with his own motives and a penchant for mischief. Fanfiction writers might explore how their different worlds collide. Maybe Loki's magic and Tony's technology could either clash or combine in unique ways. For example, they could be forced to work together against a common enemy, leading to a begrudging respect for each other.
I really like 'A Meeting of Minds'. In this fanfiction, Loki and Tony start off as adversaries but as the story progresses, they find common ground and a unique bond forms. The author does an excellent job of writing their dialogues, making it feel very real.
In fanfiction, Loki and Tony's friendship can be really interesting. They are both complex characters. Loki, with his mischievous nature, and Tony, the brilliant inventor. Their friendship might start from a mutual understanding of being different from the norm. Maybe Loki sees Tony's genius as something worthy of his respect, and Tony might be intrigued by Loki's otherworldly powers.
I'm not sure of specific 'Percy controlled by Loki' fanfictions off the top of my head. You could try searching on popular fanfiction websites like Archive of Our Own (AO3). There might be some interesting stories there that explore this unique concept.