May I ask which anime and manga did Mavis, the first president of the Fairy Tail, first appear in? What was his introduction?

Answer 1

It might not meet your needs, but I'll try my best to recommend a novel that's most relevant to your description: Marvel: The Beginning and Fury Steals the Director. This book is a light novel by the author Bu Xiangzhi. It's a derivative doujinshi novel.

The system quest wanted me to be the director of Marvel. I rejected it at first, but it gave me too much. [Justice has drawn Seljubikitas-Self-Slash!] [Crimson Eye] Justice? Harry was confused."System, do you have some misunderstanding about justice?" The system was good at everything, but it had its own understanding of keywords. The emissary of all kinds of anime came to Marvel, and even brought the local specialties of their world, such as the Peril Species of the Crimson World, the Twelve Ghost Moons of the Ghost Destruction World, the Void Invasion of the League of Legends, the Eight Great Demons, the Weirdo Association, and the Big Wood Clan...
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"The Dark Wizard in the American Manga World" was a light novel by the author, Don't Be Reasoned. It was a derivative doujinshi novel. The general plot of this novel was as follows:

Title: My Shadow is the Power of Ten Tails. Author: It's me! Please support me, big shots. I need all kinds of nutrition to grow new books.
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"The Legend of Mei Lin" was a fantasy romance novel written by the former author, Aoyagi. The general plot of this novel was:

Mei Lin's old readers, after a period of brewing, Mei Lin has been reborn. Please search for the title of the book,"A Bloodline Warlock of an American TV Series". The pit has been dug, and I'm looking for a mistress. You can wait until you're fat before you read it. His new book,"Accidentally Became a Big Boss," was already a fat pit! Friends are welcome to collect and submit! Mei Lin, who had the best wizard talent, had become a laughing stock among her classmates because she could not break through for a long time. She was about to become a slave. An unexpected encounter had given her a wonderful treasure. Not only did it make up for the inexplicable deficiency in her sea of consciousness, but it could also turn waste into treasure through the characteristics of the treasure. She had finally successfully embarked on the path of a wizard and used her own advantages to achieve eternity!
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"The Age of Shuigo the Elf" was a light novel written by the author, the big monster in the mirror. The general plot of this novel was:

The initial elfin, Kedar Duck, was not an ordinary duck. Shugo was a little flustered. What if he was bullied by a duck on their first meeting? Online waiting for a rather urgent newbie, asking for protection…
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"The Origin of the Elves: Early Entry" was a light novel by the author, Inkwind Xiaoxiao. The general plot of the novel was:

Reader group: 371325678 [The game has swallowed up reality…The arrival of the apocalypse…Contact with the elven world…The fate of the entire world…Integration into the elven world…New unknown regions…Decaying alliances…Disruptors…Chaotic war between all forces…Reshuffling of resources…New dynasty replacement…Entering a new era!] [The Divine Beast's interference…Alpaca's conspiracy? Or is it the so-called second yuan?] [Elven date: New Era!] "Yes, yes, that's right!" [System: Foolish host, hurry up and catch the mastermind!] Mo Feng thought,[Who should I ask? How would I know how to catch them?] System: "That's your problem. I'll give you a hint. He's right above your head." Mo Feng,"Above your head?" Emmm keywords: Pokémon, Pokemon.
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The book "Dragon Egg Joins the Chat Group at the Beginning of the Game" was a light novel, a derivative doujinshi novel, written by the author, Dumbo, who loved to eat. The general plot of this novel was:

He pushed down his new book, Comic Comic, About Me Becoming a Slime. Meeting in a different world, you have unlimited potential. In the dark sewers, a slime was silently born. It had a flexible moral bottom line. To some existences, it was absolutely evil, but it was also the only salvation. A brand new future was born in the destruction. He was the absolute Demon King, the Lord of the Seven Deadly Sins, the King of Demons... Slime! After transmigrating into the Dragon Spirit Clan in the game, the cheat system activated the chat group at the same time. In the early stages, there were things like reincarnating into a spider, searching for a chance encounter in the Dungeon, Ultraman Diga, Fantasy Village, and later on, there would be the addition of the leisurely daily king, the dragon maid of the Lin family, Xiu Liao, the demon's tail, the long charcoal, the fox demon, under one person, the assassin Wu Liuqi, and some of his favorite anime and novel characters. The main character would not pretend to be a prophet and forcefully lower the intelligence of other characters.
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"From the Beginning of Becoming the Lord of Monsters" was a light novel by Salted Fish and Rice, a derivative Doujinshi novel. The general plot of the novel was:

The new book,"Don't even think about trying to kill me", has been released. Please collect it, please vote…Current travel route: Original Creator World-Blade of Ghost Destruction-Original Creator World-The grandson of the slippery ghost-Reincarnated Slime-Battle of the Holy Grail-Blessing for the beautiful foreign world-Problem Child-When Bone King met the demon, a handsome young man with two horns and waist-length red hair led the hundred demons at the front. Dark Dou: "Actually, I really don't want to be the Lord of Monsters. There's no profit in this profession at all. My dream is to become a charlatan…Ptui, to become a great Yin-Yang Master." [The demons: My lord, wake up! You are the leader of the demons!]
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"The Demon's Tail: The Strongest Magic Shooter" was a light novel written by the author, Xiao Yuanyou. It was a humorous and sarcastic novel. The general plot of this novel was:

Xiao Rang, a university graduate, was obsessed with the anime "Fairy Tail". He spent a lot of time collecting related pictures and addicted to derivative games until he died suddenly in the game. He transmigrated to the world of Fairy Tail and was reborn as the dragon Sodier. He took risks with his idols, played with them, and played with them. "Sodier, let's go to work!" Naz shouted. "Haha! "I'm not writing anymore. Naz and the others are urging us to set off…"
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"The King of Arora Island at the Beginning" was a light novel that the author had long wished to write. The general plot of this novel was:

Meteor, who was summoned to the Elf World by Naikrozma, shouldered the heavy responsibility of healing him. But why did Kapu Moo choose me to be the king of the island when I just came out? Hey hey hey, I don't even have a single elf! [Integration of world views, reference animation, special chapter, various comics] keywords: Pokémon, Pokémon
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"The Elf Envoy from the Demon Tail" was a light novel written by the author, Dancing Starry Sky. It was a derivative doujinshi novel. The general plot of the novel was:

The young man who obtained the Elf System descended into the world of the Fairy Tail and dominated the world as an elf sorcerer. The introduction is too weak, please enter and take a look!