In a crossover with 'Fullmetal Alchemist', Edward Elric could be an interesting addition. His knowledge of alchemy and his quest for the Philosopher's Stone could intersect with the Goblin Slayer's world in unexpected ways. From Goblin Slayer, Dwarf Shaman could be included. His knowledge of runes and magic could complement Edward's alchemical skills, and their interactions would be full of banter and learning.
Obviously, the Goblin Slayer himself is a must - he is the central figure. The Priestess is also great to include as she often accompanies the Goblin Slayer and provides support with her healing and purification magic. Her naivete and growth throughout the story can add depth to the fanfic.
One idea could be a crossover with 'Sword Art Online'. The Goblin Slayer could be transported into the virtual world of SAO where he has to deal with goblin - like mobs in a different gaming environment. He might use his unique skills and no - nonsense attitude to clear floors and quests in the game.
In a crossover with 'Attack on Titan', Eren Yeager could be an interesting addition. His determination and ability to transform into a Titan could be used in tandem with the Goblin Slayer's tactics. They could face off against goblins that have somehow made their way into the walls, or maybe even goblins that have been experimented on by the same people who created the Titans.
One interesting aspect could be the contrast in their fighting styles. The Goblin Slayer is more methodical and strategic when dealing with goblins, using his knowledge of their habits. The Doom Slayer, on the other hand, is a force of pure destruction. In a crossover, perhaps they could learn from each other. The Goblin Slayer could pick up some of the Doom Slayer's more aggressive tactics, while the Doom Slayer might gain some strategic thinking from the Goblin Slayer.
Obviously, the Goblin Slayer himself would be one of the main characters. From Destiny, the Guardian, especially a Hunter with their stealth and agility, could be a great match. The Hunter's ability to quickly dispatch enemies and traverse difficult terrain could complement the Goblin Slayer's more brute - force approach when it comes to goblin - slaying.
If it's a crossover with 'Naruto', Naruto Uzumaki would be an interesting character to pair with the Goblin Slayer. Naruto's positive attitude and his powerful ninja skills could complement the Goblin Slayer's more serious and direct fighting style. They could work together to protect a village that is being attacked by goblins. Also, in a crossover with 'One Piece', Luffy could be paired with the Goblin Slayer. Luffy's determination and his ability to lead his crew could be useful when they are facing a large group of goblins.
Sebastian is often a popular choice. His demonic nature and his loyalty (in a rather twisted way) to Ciel make him a very interesting character to cross over. He can easily interact with characters from other dark or supernatural works, and his powers and suave personality can add a lot to a crossover story.
I can't specifically recommend Goblin Slayer lemon fanfics as they often involve adult - themed or inappropriate content. Instead, consider looking for non - lemon fanfics. You might find some great ones that explore the relationships between the characters in a more appropriate and creative way, like how Goblin Slayer and Priestess's friendship could develop further or how the other characters interact with the main character in different quests.
There could be a cultural clash. The Doom Slayer comes from a more futuristic and hellish setting, while the Goblin Slayer is in a medieval - ish fantasy world. Their ways of communicating and understanding the world are different. However, this could also lead to some interesting exchanges. For example, the Goblin Slayer might be fascinated by the Doom Slayer's energy - based weapons, and the Doom Slayer could be intrigued by the magic and alchemy in the Goblin Slayer's world.
Yes, the Goblin Slayer light novel is popular. Its engaging plot, well-developed characters, and exciting adventures have made it a favorite among fantasy lovers. Moreover, its adaptation into anime and other forms has further increased its popularity.