The boy was poisoned by snake venom

"The Rebirth of the First Daughter: The Snake Queen Is Not to Be Trifled With" meets your requirements! The male protagonist could command the snake, and the female protagonist could control the snake. The two of them worked together to help each other and seek power in the palace. I hope you like this fairy's recommendation. Muah ~😗

One unique aspect is the way the story can blend the themes of both universes. The Metal Gear series often has themes of war, espionage, and the cost of conflict. RWBY has themes of friendship, growing up, and fighting against evil. In the fanfic, these themes can intersect. For instance, Venom Snake might have to learn about the importance of friendship in RWBY while also teaching the RWBY characters about the harsh realities of war and survival that he has faced in his own world. This creates a rich and complex narrative that is different from either of the original universes on their own.

One great example could be a fanfiction where Venom Snake and Quiet form an unexpected alliance during a mission. They start to understand each other's motives and pasts, which deepens their connection. Quiet's silent nature might be explored in contrast to Venom Snake's more stoic exterior, creating a unique dynamic.

There's a fanfic called 'Venom Snake: RWBY's Unlikely Ally'. In this one, Venom Snake finds himself in the RWBY universe and has to team up with the main characters. It shows how his combat skills and strategic thinking from the Metal Gear series can be applied in the RWBY setting. He has to face off against Grimm while also dealing with the politics and power dynamics within the RWBY world.

There could be a Venom Snake crossover fanfiction set in a post - apocalyptic world where he meets characters from other survival - themed franchises. In this type of story, Venom Snake's combat and survival skills would be put to the test in a completely different environment, and the author could explore how he adapts and forms new alliances.

Survival is also a prevalent theme. Given the nature of the Metal Gear universe, fanfics might depict Quiet and Venom Snake relying on each other to survive in hostile environments, whether it's facing enemy forces or the harsh natural elements. They may have to work together to overcome various challenges, which in turn deepens their bond. And sometimes, there could be a theme of sacrifice, where either Quiet or Venom Snake is willing to put themselves in danger for the other's sake.

One use could be in extremely powerful dark magic spells. Since basilisk venom is so deadly, a wand poisoned with it might be able to amplify curses to a greater degree. For example, the Killing Curse could potentially be made even more lethal or difficult to resist.

A common theme is trust. Since Quiet has her own secrets and Venom Snake has his, fanfictions might focus on how they gradually come to trust each other. It could start with a simple act of cooperation in battle and then develop into a deeper level of mutual reliance. Also, the theme of sacrifice might be present. For example, one of them might be in a situation where they have to sacrifice something for the other.

The moral is often 'Beware of the evil in disguise'. Just like the snake in the story, it might seem harmless at first but can turn out to be very dangerous.

The moral could be 'Beware of the danger that can lurk in the most unexpected forms'. Just like the snake in the story, which might seem harmless at first but could turn out to be a threat to the boy.