It could be a street - smart Parisian. Someone who has witnessed all the strange happenings in Paris related to the Miraculous but from a civilian's perspective. This person might have noticed patterns and details that others have missed. They could offer Gabriel practical advice based on their observations, like how the heroes operate or where the Miraculous might be hidden. Their knowledge, though different from the magical knowledge Gabriel might be used to, could still be very valuable in his pursuits.
Maybe the guide is a time - traveler. Someone from the future who has seen the consequences of Gabriel's actions and comes back to try and change the course of events. This time - traveler would know all the ins and outs of what's going to happen and could guide Gabriel towards making better choices. They could show him the destruction his actions as Hawk Moth will cause and offer him an alternative path to achieve his goals in a more positive way.
One possible plot could be that Gabriel Agreste, in his search for a way to achieve his goals (maybe related to his fashion empire or his secret identity as Hawk Moth), gets help from an unexpected guide. This guide might be a character who has unique knowledge of the Miraculous or the hidden aspects of Paris. For example, the guide could be an old acquaintance who has connections to the magic that surrounds the Miraculous. They might lead Gabriel to discover new powers or secrets that could change his approach to his plans.
It could be an unknown villain from another dimension. Somebody with a lot of knowledge about dark magic and villainy.
It could be a character from a different dimension or realm. This character might have some sort of connection to the Miraculouses and sees potential in Hawkmoth. They decide to help him, thinking that they can redirect his actions towards a more positive outcome, or at least a less destructive one.
Well, perhaps Gabriel discovers that Adrien has been secretly helping Ladybug and Chat Noir. This betrayal, in his eyes, could lead to his akumatization. As an akumatized villain, he might have the ability to create dark illusions of everyone's worst fears. He uses these illusions to try and break the will of the superheroes and force them to reveal their identities. He could also use his power to turn the citizens of Paris against Ladybug and Chat Noir, making it even more difficult for them to operate.
Well, Hawkmoth might become more powerful. Maybe the villain guide teaches him new ways to manipulate people or use his powers more effectively.
It could be Lila Rossi. Since she's a master manipulator, she could find out about Gabriel's identity as Hawkmoth. Maybe she tries to blackmail him into doing something for her, but Gabriel refuses. In retaliation, she somehow manages to get an akuma and send it to Gabriel, causing his akumatization. Lila might think that by akumatizing Gabriel, she can gain more power and control in Paris.
There were a few novels that he could recommend. Among them were " Boyfriend Strategy Guide "," Ex-boyfriend Strategy Guide "," After binding to the system, I defeated my ex-boyfriend "," After the system wants me to defeat the big boss 'ex-boyfriend "," Ex-boyfriend Strategy Guide "," Fighting Boyfriends ", and so on. These novels covered different plots and topics to satisfy different readers 'preferences. As for which novel is suitable for you, you still need to choose according to your personal reading preferences.
I'm not sure specifically as I haven't read this particular fanfiction. But the guide could be someone with special powers or knowledge. Maybe Hawkmoth gets help like strategic advice or some form of magical assistance to further his evil plans.
One great fanfiction is 'The Secrets of Gabriel Agreste'. It delves deep into his motives and the backstory that we don't often see in the show. It gives a more complex view of his character.
In the 'Chat Noir Confronts Gabriel Agreste' fanfic, Chat Noir might finally expose Gabriel as Hawkmoth. He could use his cataclysm to threaten Gabriel into revealing his true identity and his motives for being Hawkmoth. This would be a huge turning point in the story as it would end the mystery that has been building up throughout the series.