Dragon Crests (HTTYD)

The Dragon Crests signify the seven dragon classes and Viking Tribes that use dragons as their mark.

Appearance
The crests take the form of dragons in the Archipelago.

Lore
Each crest has their own history with their tribe and dragons that their based on.
 * Dragon Classes: Seven kinds of dragons serve as the mark(s) of the class of dragons. Stoker (Monstrous Nightmare), Boulder (Gronckle), Fear (Hideous Zippleback), Sharp (Deadly Nadder), Tidal (Scauldron), Mystery (Changewing) and Strike (Night Fury).  The marks can be seen in the Book of Dragons and Fear class became Tracker class when HTTYD2 came out.  (When the crest would get 'updated' into a different dragon is unknown)
 * Hairy Hooligan Tribe: Berk uses the Timerjack dragon as their mark and place it on the cover of the Book of Dragons. For the reason why they use a sharp class dragon is unknown, it's possible that the Viking that discovered Berk faced one before he could make the island his or her home.
 * Berserker Crest: Dagur's tribe use a Skrill (a Strike class dragon) as their mark. The tribe was said to have enslaved Skrills by using them lightning shooting weapons, when or who stopped it is unknown.
 * Drago Bludvist: Drago's armada have more than one kind of dragon(s) on their sailors, most of them look like Monstrous Nightmares.

Some tribes, like the Outcasts don't use dragons as their mark and some Vikings like to place different kinds of dragon marks on objects like Shields, Flags, Totem poles (mostly in School of Dragons), Sails, Belts and Books.

Role in the Crossover
While that are the crests of tribes and dragon classes, fans see the Strike Class mark (or the one on Toothless' red tailfin) as Hiccup's RotBTD crest, much like how Corona's sun crest is associated with Rapunzel Corona and DunBroch's crest is Merida DunBroch's.