One possible plot could be that Voldemort initially doesn't believe Harry. He might think it's a ploy by Harry to create discord among his Death Eaters. But then he starts to suspect Snape when he recalls some of Snape's past actions that seem a bit off in the context of loyalty to him.
Perhaps Voldemort would immediately act on the information. He could summon Snape and start interrogating him. Snape, being a skilled Occlumens, would try to hide his true intentions and loyalties. This could lead to a tense stand - off between Snape and Voldemort, with Harry watching on, not entirely sure what he has unleashed.
In the fanfiction, it could also be that Harry tells Voldemort about Snape as a last - ditch effort to save someone he loves. Voldemort, after hearing this, might use Snape as a pawn in a new and cruel scheme. Snape, on the other hand, would be forced to make some very difficult decisions about his allegiances and actions. He might try to find a way to turn the situation around and still protect Harry and Hogwarts in the end.
In a fanfiction scenario, Harry's actions could cause a complete breakdown in any potential for a positive relationship between them. Snape's loyalty to Dumbledore and his role in protecting Harry from the shadows would be put at risk. Harry would have to face the fact that he may have made a huge mistake. And Snape, who has sacrificed so much already, would be in an even more precarious position, both with Voldemort and in the wizarding world in general. This could lead to a chain of events that completely alters the course of the wizarding war, with far - reaching consequences for both Harry and Snape.
Snape could be in great danger. Voldemort might immediately try to kill him. Snape would have to fight for his life or try to escape. His status among the Death Eaters would be completely ruined, and he'd become a hunted man.
One possible reason could be that Snape fails to deliver crucial information. Voldemort is a very demanding and unforgiving master. If Snape doesn't give him accurate details about the Order of the Phoenix's plans, for example, Voldemort would surely be enraged and punish him.
Well, one possible plot could be that Sirius tells Snape about Remus being a werewolf in the fanfiction. This revelation might lead to a series of events where Snape tries to use this information against Remus, but Sirius steps in to protect his friend. Maybe there could also be a sub - plot about how the wizarding community reacts to this leaked information.
Yes, there are some fanfictions with such out - of - the - box concepts in the Harry Potter fanfiction community. However, these are not in line with the original story's canon.
It could be that Voldemort's pet Harry is actually a form of psychological warfare for Voldemort. He wants to break Harry's spirit completely. However, Harry uses this situation to his advantage. He befriends some of the dark creatures that Voldemort has around his lair, and with their help, he manages to create chaos and confusion, which in turn gives the Order of the Phoenix an opportunity to strike at Voldemort.
One possible plot could be that they are forced to be partners to save the wizarding world from an even greater threat. Maybe an ancient evil that neither of them can face alone. So, they have to put aside their differences and work together, which would be a huge change from their usual enmity.
In a 'harry joins voldemort fanfiction', perhaps Harry discovers a dark secret about the wizarding world that makes him think Voldemort was right all along. It could be something about the Ministry of Magic being corrupt and Voldemort's way of ruling, although extreme, is the only solution. So he joins Voldemort to 'fix' the wizarding world.
There are many ways this could happen in fanfic. One way is that Harry uses his connection with Voldemort's mind. Since Harry has a link to Voldemort's thoughts, he might be able to pick up on Voldemort's doubts about Snape. And then Harry starts to investigate Snape further. He might recall some strange actions of Snape in the past, like his ambiguous loyalty during certain battles or his secret meetings with some unknown figures. Combining all these, Harry eventually realizes that Snape is a spy.
For Harry, saving Snape could make him more empathetic towards Snape's past actions. He might start to understand the complex web of loyalties that Snape was caught in. It could also make Harry more confident in his ability to make moral decisions independent of others' opinions.