Yes, there might be such fanfictions out there. The Harry Potter fandom is vast, and fans often explore dark and dramatic scenarios in their works. However, these can vary greatly in quality and adherence to the spirit of the original series.
There could be themes of trauma and recovery. If Harry is tortured in front of Ginny, both of them would likely experience significant trauma. The fanfiction could explore how they deal with that, both individually and as a couple. Also, themes of loyalty and friendship might be present as their friends try to rescue Harry.
This kind of scenario in fanfiction often plays on the emotions of the readers. It might make Harry seem more heroic as he could potentially try to stop the torture. On the other hand, it could also show Draco in a more vulnerable light, which is different from his usual haughty self. The fanfiction author might be using this situation to build a bridge between the two characters, who are often on opposite sides in the original series. It could also lead to a whole new arc in the fanfiction where they team up against a common enemy because of this shared traumatic experience.
One possible motive could be to create an emotional shock for Harry. It makes him face a difficult situation and tests his moral compass. Another motive might be to force Draco to reveal some important information, with the torturers knowing that Harry's presence would add extra pressure on Draco.
I'm not sure specifically as I haven't read that particular fanfiction. But generally, it might involve Ginny facing some form of cruel treatment by the Carrows in a fictional and often dark scenario created by the fanfiction writer.
One thing to keep in mind when looking for such a fanfic is that it might be a bit hard to find as it's a rather specific and dark concept. Some fanfic writers might be hesitant to write about such extreme torture scenarios. You could also check fanfic communities or forums dedicated to Harry Potter. Post a request there asking if anyone knows of a fanfic with this plot. Maybe someone has come across it or has even written one themselves.
In this fanfiction, it might be that the gods are influenced by an external dark force. This force convinces them that Percy is a threat. So, instead of a fair trial, they torture him in front of everyone. Percy, being a hero, would probably endure it with great courage and his friends might be on a quest to prove his innocence and save him from this unjust situation.
It could be Ares. He's always been sort of a hot - headed and war - loving god. Maybe he's jealous of Percy's popularity among the demigods and wants to see him suffer. So he manipulates the other gods into believing Percy has done something wrong and that he should be tortured.
One reason could be to explore the extreme emotions that such a situation would evoke. It would show the depth of the relationship between Harry and Sirius, and how Sirius would react seeing Harry in pain. It also adds a layer of drama and darkness to the story, which can be appealing to some readers who like more intense and edgy fanfics.