In some Pokémon Ash tied up fanfictions, the situation is more of a misunderstanding. Maybe a group of new trainers thought Ash was a poacher because he was in an area that was restricted for a special Pokémon breeding ground. So they tied him up. Ash then has to explain his situation and his love for Pokémon to them. This type of fanfiction often delves into Ash's character, showing his passion for Pokémon and how he can turn a bad situation into a good one by making new friends among the trainers who initially mistook him.
Team Rocket is the most likely candidate. They've always been after Ash's Pikachu and tying him up would be a way to stop him from protecting his Pokémon. They could use ropes or some kind of Pokémon - powered restraining device.
One possible plot could be that Ash gets tied up by a group of Team Rocket grunts who manage to outwit him. They tie him up to stop him from interfering with their latest evil plan to steal rare Pokémon. His Pokémon then have to work together to free him and foil the villains' scheme.
There are fanfictions where Ash is made unconscious by a mysterious villain's attack. His Pikachu then takes on a more protective role, trying to find a way to revive Ash. Some fanfictions in this theme also explore the emotional turmoil of his friends like Misty and Brock when Ash is in this state. They might search for rare herbs or items to help him wake up.
There's a fanfic where Ash is a coordinator and he uses his Charizard in contests. This is interesting because Charizard is known for its power in battles, but in this story, Ash has to transform it into a more elegant and performance - worthy Pokemon. He has to work on Charizard's attitude too, as it's not used to the finesse required in coordinator events. Ash uses his bond with Charizard to bring out a side of it that no one has seen before in the context of contests.
One good example could be a story where Ash and Tenten team up in a Pokémon tournament. They combine their skills, with Ash's Pokémon knowledge and Tenten's ninja - like agility and strategic thinking to outwit their opponents.
Well, there's a fanfiction where Ash is a scientific genius. He starts to study the genetic makeup of Pokemon and finds a way to enhance their natural abilities. This makes his battles not just about training but also about scientific innovation. Also, there are fanfictions where he uses his smartness to solve mysteries in the Pokemon world, like the mystery behind some rare and powerful Pokemon that are said to hold the key to a great power.
I'm not sure specifically about 'Quilava Pokemon tied up' fanfics as this is a rather specific and perhaps not very common theme. You could try searching on popular fanfic websites like FanFiction.net or Archive of Our Own. Maybe start with general Quilava fanfics and then see if there are any that involve the situation you're interested in.
A fanfiction could be about a legendary Pokemon being tied up by an ancient spell or curse. This would set up a story where the trainer has to find a way to break the spell and free the Pokemon. Maybe in the story 'Legendary in Bonds', the trainer has to go on a quest, facing various challenges and learning about the Pokemon's past, all while the Pokemon is in this tied - up state, creating a sense of urgency and adventure.
One interesting Pokemon tied up fanfiction could be about a trainer's Pokemon getting tied up in a tricky situation during a mysterious dungeon exploration. For example, Pikachu might get tied up by some strange vines in an ancient forest while the trainer has to figure out how to free it without causing harm. Another could involve a group of Pokemon being tied up by a villainous team, and their struggle to break free and save the day.
A great fanfiction could be the one where Anabel is in trouble and Ash comes to her rescue. This heroic act makes Anabel see Ash in a new light, and from there, their love story begins. Some fanfics also explore how their different personalities complement each other. Ash's adventurous spirit and Anabel's calm and collected nature create an interesting dynamic that draws them closer in the story.