Hiccup has the Night Fury’s blood on his hands and he feels like he’s killed a part of himself. He stands up. He can’t catch his breath. He can’t grasp his surroundings. He might be having a panic attack.
"I did it. I’m a viking. I’m a viking…!” he says and tries to instill pride in himself. It works, to an extent. His overactive imagination springs to life and he smiles despite his squirming gut and pulling brow. Despite the sickness and self-loathing.
He walks home. The giant Night Fury heart is warm in his hand, dripping a war-trail in his wake. The blood is green—dragon’s blood—but the ventricles and make-up are so similar to a human’s that Hiccup has to stop and puke into a bush twice.
He makes to the village, thrusts the humanlike heart into his father’s face, and then—predictably—takes his father and crew to the dragon’s body for further proof. He stops several feet away. He can’t step any closer. It feels like he’s intruding on his own grave. He feels cursed.
Despite what he feels, Hiccup is celebrated. Snot and the twins and Fishlegs ask him a thousand questions. His father slaps his back, hugs him, states his pride. Gobber claims he “knew it”. Astrid starts looking his way. Not yet smiling, but her eyes are open to consideration. She’s watching him and a part of him really, really likes it. He starts to heal from the deep, emotional trauma of killing himself. He heals for her. For his father. For his tribe.
Everyone is watching him and Hiccup is both Terrified and Pleased. His mistakes are better documented but also better forgiven. He gains leniency like he’s never had before. Every invention goes into killing dragons to maintain it; what other choices does he have? He downed a Night Fury and it gave him everything he “wanted”. Even though his dreams always, always, have those eyes—its eyes—pleading for mercy, and it continues to tear at his soul.
He starts seeing Astrid. She takes his weapons seriously, as does Gobber, as does his father. She whispers encouragements, assures him he’s doing the right thing, erases the insecurities of his dreams and he keeps at it.
Over the weeks, Hiccup’s guilt ebbs and his pride takes over. The praise of the village, of his father, of her, overrides the haunting imagery of those eyes. He focuses on his hypothesis. On his studies. His newfound freedom and respect gives him the leverage he needs to move up in the village.
That moment he had with the Night Fury—a fraction of understanding—makes him curious about the other dragons—if they would give him the same reflection—but his popularity interferes. Hiccup feels an intense pressure to keep measuring up to what his village expects.
He can’t do it in the day-light, but at night, as everyone’s asleep, he’ll visit the cages. He’ll whisper to the dragons and try and record their responses. He can’t shake the idea that there’s human-like intelligence at their end. That they can respond to him.
His father is optimistic in finding the Red Death… before the ice-sets-in. Hiccup advises against it. Stoick listens. His son killed a Night Fury. His weapons have merit. His methods have an endgame.
Slowly, over the winter months, Berk grows stronger. Using Hiccup’s weapons, they gain leverage over the dragons. Their frienemies—the Bogs, the Meatheads, even the Outcasts—have no choice but to turn to Berk in its prosperity. They start to buy out Hiccup’s inventions. The plans for them. It becomes a franchise. Over the next several years, thousands… nearly millions…of dragons are killed. Hunted to extinction. The Green Death slowly starves.
Hiccup marries Astrid, he rules Berk, he spends the rest of his life grounded as a wealthy, successful, cunning chief.
But he never touches the skies, as he once did in his dreams.