In some fanfictions, Natsu's dragon slayer magic and Mavis's Fairy Law could be combined in a unique way. For example, Natsu could use his fire to enhance the power of Mavis's Fairy Law, making it more destructive against their enemies.
Fan writers might come up with a scenario where Mavis uses her magic to enhance Natsu's physical abilities. Since she has a deep understanding of magic, she could find a way to make Natsu's attacks even more powerful. Maybe she could use her magic to increase the intensity of Natsu's fire, or make his body more resistant to damage while he's using his dragon slayer powers.
Well, in many fanfictions, their relationship might start with Natsu being a bit in awe of Mavis as she is a very important figure in Fairy Tail's history. Natsu, being his brash self, might initially make mistakes around her but gradually learns from her wisdom. As time goes on, he could come to respect her even more deeply and they might form a bond where Mavis becomes like a guiding light for Natsu in his adventures and growth within the Fairy Tail guild.
In many fanfictions, Natsu's fire magic and Brandish's size - manipulation magic can create interesting interactions. For example, Brandish might reduce the size of a large fireball Natsu creates to use it more precisely against an enemy. Or Natsu's intense heat could potentially disrupt Brandish's magic if she's not careful when they are in close combat. Their powers can also be combined in a more creative way, like Brandish making a small opening in a large object and Natsu shooting his fire through it to hit a target that was previously unreachable.
There are stories where Wendy uses her sky magic to enhance Natsu's senses. Since she has a connection to the sky, she can heighten Natsu's vision or hearing, which helps him in a battle. And in return, Natsu protects Wendy from any close - range attacks while she's using her magic to support him, creating a symbiotic relationship between their powers.
One possible plot could be that there is some sort of misunderstanding or dark magic at play that causes Natsu and Mavis to fight. Natsu, being hot - headed, jumps into the fray without fully understanding the situation. Mavis, on the other hand, is trying to figure out a way to stop the fight without harming Natsu. As the battle progresses, they both start to realize that they are being manipulated and then team up to face the real enemy.
In fanfiction, Natsu and Mavis could be like a mentor - mentee relationship. Mavis being the first master of Fairy Tail has a lot of knowledge and wisdom. Natsu could look up to her and she could guide him in his journey, much like how Makarov guided him in the main story.
Naruto has his Nine - Tails chakra which is extremely powerful. If Lucy were to use her magic to somehow channel that chakra into a new form of attack, it could be very effective. For example, she could create a magic circle that concentrates the Nine - Tails chakra and then release it as a beam of energy. Or perhaps Naruto could use his chakra to enhance the abilities of Lucy's spirits. He could transfer some of his chakra to a spirit she has summoned, making it faster, stronger, and more durable, while the spirit could use its own unique abilities to help Naruto in combat, like a flying spirit could give Naruto aerial support during a fight.
In a fight between Natsu and Mavis in a fanfiction, it's really hard to say who would win. Natsu is extremely powerful with his dragon slayer magic, being able to take on some really tough foes. However, Mavis is the first master of Fairy Tail and has a great deal of wisdom and powerful magic herself. It could really go either way depending on how the fanfiction writer wants to portray the battle.
One unique plot point could be Natsu having to learn magic in a completely different way under Mavis' tutelage. Instead of his usual hands - on, instinctive approach, he has to study theory and history. Another could be Mavis using Natsu to revive some long - lost traditions of the Fairy Tail guild. Maybe Natsu discovers a hidden power within himself that was dormant until Mavis guided him.
The crossover can also lead to new power - up scenarios. For instance, if they face a very strong enemy together, they might combine their powers in a unique way. Naruto could provide the raw power and speed, while Mavis uses her strategic mind and magic to direct and enhance that power. This could result in a new super - form or ability that neither of them could achieve on their own.
In some fanfictions, he is a mentor - like figure. He teaches Mavis or other young wizards important lessons about magic, life, and the values of Fairy Tail. This could include things like the importance of friendship in magic, which is a central theme in the Fairy Tail series.