It would be a very strange and dark turn of events. Maybe they would try to rule the wizarding world together in a more 'balanced' way, but it's hard to imagine Harry giving up his values so easily. It could also lead to a completely different kind of magic system emerging as they combine their powers and knowledge.
In a 'Harry Potter and Voldemort team up' fanfiction, the plot could involve a prophecy that states only the combined power of the two can save the wizarding world from an upcoming cataclysm. At first, they are reluctant, but as the signs of the impending doom become more evident, they put aside their differences. They use their combined magic to unlock ancient secrets and find magical artifacts that are needed to prevent the disaster. This new alliance also causes a major shift in the power dynamics and relationships within the wizarding world.
It's possible. In the realm of fanfiction, the imagination knows no bounds. Writers might come up with such a scenario for various reasons, perhaps to explore a different side of the characters' relationships. But it's not a common or mainstream concept within the Harry Potter fanfiction community, as it goes against the typical character dynamics we expect from the series.
In many fanfictions, Harry Potter squinting at Voldemort could be a sign of intense focus. It might be that Harry is trying to read Voldemort's next move, or perhaps he's looking for some sign of weakness. For example, in some stories, Harry's squinting could be related to his newfound magical abilities that he's using to analyze Voldemort's magic signature.
In this fanfiction, it could be that Voldemort has a premonition. He sees that if Harry Potter dies, it will lead to a series of disasters that will also destroy his own plans. So, in order to preserve the balance or to keep his long - term goals intact, he saves Harry. For example, if Harry's death causes an uncontrollable chaos in the wizarding world, Voldemort's rule over the dark forces might be disrupted. So he steps in to save Harry.
A group of rogue Death Eaters could be the main antagonists. They think that Voldemort has gone soft by teaming up with Harry. So they break away and form their own more extreme and violent group. They start attacking both the wizarding world and anyone associated with Harry and Voldemort's new alliance. Harry and Voldemort must then fight against their former allies who have become a greater threat than ever.
The wizarding world might be in shock. People who have always seen Voldemort as the ultimate evil would be confused. They would have to re - evaluate their views on Voldemort. Harry, on the other hand, would be in a very strange situation. He might be distrusted by some of his friends who think he has made a deal with Voldemort.
The relationship would become extremely complex. Harry would be confused and conflicted. He's been taught all his life that Voldemort is pure evil, but now he's been saved by him. Voldemort, on the other hand, might start to see Harry in a different light, perhaps as a tool or as someone with whom he can form an unusual bond. It would be a relationship full of mistrust on Harry's part and manipulative intentions on Voldemort's.
The relationship would become extremely complex. Harry would no longer be able to simply see Voldemort as pure evil. He would be in a state of confusion and moral dilemma. Voldemort, on the other hand, might start to view Harry as a more interesting pawn rather than just an enemy to be killed. They could develop a strange sort of respect for each other, at least on a surface level.
No. This is a very unorthodox concept that is not likely to be popular in the mainstream Harry Potter fanfiction world. Most popular fanfictions tend to follow more traditional storylines like the battle between good and evil, or the relationships between the main characters.