There were only two reasons Natsu could think of that made Zeref's command make sense.
The first: Zeref was ordering him to fly to his death. Natsu was starved and weak, barely able to manage the flight there. Fairy Tail would see him coming, and if they didn't shoot him down, it wouldn't take much longer for them to kill him. Zeref was sentencing him to die, with the added bonus of Lucy seeing it all, shattering her heart because he was unable to shatter her body.
The second: Zeref did want him to marry Lucy. His brother wanted him to marry her so that when they came together to be wed, he would be close enough to finally kill her.
Well, she'd be close enough to kill Zeref too.
So Natsu flew to Fairy Tail.
Zeref had sent sparks of magic to lick at his feet when he first hesitated to take flight. His brother had offered him no explanations as to his desire for Natsu to propose to their enemy. He'd merely told him- laughing all the while- that should she accept, they were to come together under the full moon in a months' time. His brother had been whipping amused tears from his eyes when Natsu had finally took to the skies.
It was a gruelling effort to fly. His wings screamed in protest with every beat, spots blurred his vision the higher he climbed. If it wasn't for his destination, he knew he would have collapsed long before half way. He was sure it was more than his exhaustion weighing him down. The possibilities of Zeref's plan weighed heavy on his shoulders.
His stomach churned as Makarov's castle grew closer. The grand structure was a beacon against the overcast sky, illuminated by the negations taking place inside. Natsu's keen eyes immediately picked out the guards patrolling the castle walls. It was only a matter of time before they spotted him too.
Sure enough, as he began to descend warning shouts issued from the soldiers stationed above the main gate. Natsu grit his teeth as he forced his wings to pick up the pace. Even weak and injured he was stronger than ten of Magnolia's soldiers. They had barely notched their arrows when he got close enough to take them out with a swipe of his claws.
He restrained himself though. Instead he blasted them back with a gust from his wings before diving beyond the wall and down into the castles main courtyard. He flew close to the ground, weaving through the soldiers that got in his way and knocking them clean off their feet.
He couldn't hold back the smirk it caused him.
The smirk vanished when the grand doors to the main chamber came into view. The guards had formed a barricade to keep him from their King, and the thick wooden doors had been locked and bolted.
Perhaps he'd approached this the wrong way.
Knowing it was too late to change his course and desperate to get to Lucy, Natsu pulled up just before he reached the guards and sucked in a breath. He could see the soldiers eyes widen in terror in the few seconds before he released a blast of flame from his mouth. Most managed to dive to safety at the last moment, causing the full impact of his flaming roar to hit the door to the main chamber.
The wood shattered. Screams echoed from within the hall the remnants of the door collapsed inwards. Natsu dropped to the ground, taking in a shaky breath as he furled his wings, fighting against the black spots clouding his vision. Now wasn't the time to show pain.
He straightened his back and entered the chamber.
Striding through the flames and stepping over the bodies of the fallen, Natsu faced them with a mask of stone. Court members that had come to watch the proceedings scuttled back in unconceivable terror, their contorted expressions reminding Natsu just how terrifying he could be.
