Where Does Dragon Fire Come From?

Hiccup winds up a hanging from the roman spear lodged in green deth's throat, so he doesn't die right away. He discovers where dragon fire comes from. A toothless father is seemingly motivated by how sad stoic is that his son got eight. The dragon tries to burn the village down, but he can't breathe fire because hiccup's viking helmet horns are stuck in the fire holes. And so he tries to breathe fire, and his body, his body explodes.