Some HTTYD headcanons I have!
So I recently got into silly dragon franchise, and the worldbuilding is just so good that I can't stop myself from headcanoning about the dragons themselves
Red death (the huge dragon from the first film) is parasitic. The mixed pack structure we see in the first film is NOT normal. Red deaths lay eggs in known dragon nesting grounds, and when the other babies hatch, the red death is looked after by the parents (similar to cuckoo birds). As they grow, they influence other dragons to come to the nest and care for them, until it becomes a hive mind serving the red death.
Lycanwings are real, but it's a co dominant gene. 2 copies allows you to turn into a dragon from a certain age, one copy requires a dragon bite to transform for the first time, which is where the myth of lycanwing bites came from. One copy of the gene allows you to intuitively understand dragons (like hiccup and valka)
Monstrous nightmares have a dominance based social system, with everyone having a place in the pecking order, similar to chickens and horses. This is why hookfang enjoys being put face-first into the dirt by snotlout, it's a reminder who's in charge.
Also on monstrous nightmares, they set each other on fire as bonding activities to avoid their pack mates burning out. Again, this is why hookfang sets himself on fire when snotlout is riding him, to keep him from burning out/dying
Gronkles and hotburples are hard to hit/kill because of their extremely tough scales. Their scales are tough because of their diet of rocks, extra minerals and metal content that isn’t digested is shed into the scales, similar to carotenoids moving to/turning flamingo feathers pink.
In defenders of Berk, Stoick has a metal bowl. Metal is also shown to be in short supply when Gobber buys it in bulk from Johan. I think refined metal is easily accessible by gutting dragons like gronkles, harvesting smokebreath nests, etc. When Berk killed dragons, it would be an extremely common resource (explaining the bowls, forks, and occasional metal pitcher in the shows), but after, they had no way of mining and refining it themselves. This is also why meatlug's gronkle iron became as popular as it was.
