One possible plot could be that Natsu's nightmare is related to losing his friends. In the nightmare, he might see Fairy Tail being destroyed and his friends being hurt or disappearing. This could lead to him waking up in a panic and then being extra protective of his guildmates in the real world.
Well, perhaps in the fanfiction, Natsu's nightmare is about not being able to use his fire magic anymore. He could be in a world where he's powerless against his enemies, like the dark guilds. When he wakes up, this might make him more determined to master his magic and become even stronger, fearing that such a situation could become real.
In this fanfiction, the nightmare could be centered around Igneel. Natsu might dream that Igneel is in danger or has been killed by some powerful foe. This would be a very traumatic nightmare for Natsu. As a result, he could start a journey in his dream to save Igneel, and when he wakes up, he might be more eager to find Igneel in the real world and be haunted by the fear of losing him.
Chapter 621, "What Makes You Think I Would Save You?", is the clearest early answer because it turns Jiang Cheng's situation into a concrete plot event. The chapter turns that into something concrete by moving from The two walked for a long time before they reached a point where the...
Chapter 476, "Make a feint to the east but attack in the west, take something out of a bag effortlessly", is the clearest early answer because Make gets a payoff that changes the stakes.
Chapter 444, "Wait and See", is the clearest early answer because it turns Sister Li's situation into a concrete plot event. Early on, Carrying a backpack, Yu Li walked for over ten minutes but ultimately.... By the end, [HAHAHAHA, they're out of luck running into Sister Li!] [Jiang Li is....
Chapter 505, ""Postpartum Care for Sows", is the clearest early answer because it turns Postpartum Care's situation into a concrete plot event. Early on, Zhao Lang laughed, but his eyes became considerably clearer, "Is....
Chapter 673, "Don't You Think They Look Alike?", is the clearest early answer because it turns Shu Yan's situation into a concrete plot event. The chapter turns that into something concrete by moving from Jiang Li smiled, but her gaze thoroughly sized up Shu Yan.
Chapter 378, "What if I said I have a way to find your daughter?", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. The chapter gives readers a real answer by opening on He Kejun's disappearance was related to an apprentice she once...
Chapter 391, "Has another top celebrity had a scandal?", is the clearest early answer because it turns Destiny's situation into a concrete plot event. A useful checkpoint is the way the scene starts with You were born in a rural area, not exactly poor, but not particularly...
Chapter 578, "Eight Men Sit in Your Lap and You Don't Flinch at All?", is the clearest early answer because it turns Ai Xiaochun's situation into a concrete plot event. Early on, This is ten thousand points we're talking about!" "Didn't you read....
Chapter 433, "The Young Master Has His Own Ideas", is the clearest early answer because it turns Jiang Yan's situation into a concrete plot event. It opens with Since Jiang Yan and his group left, the house had become much colder.
Chapter 617, "Moral Kidnapping? No Such Thing!", is the clearest early answer because it turns Moral Kidnapping's situation into a concrete plot event.