Furious

The Beast is the most scary,ugly,ferocious and evil of all the dragons.Its species are uknown.It is believed to be a bigger relative of the gigantic seadragonus giganticus maximus.It only appeared in How to break a dragon's heart.It was the book's main atagonist.

In How to Break a Dragon's Heart
The Beast is the main antagonist of the book.He appears when Fishlegs is kidnapped by the berserk tribe and they attempt to use him as a food for the beast.However,Hiccup,Toothless and his friends come to save Fishlegs.After a long battle,they finally manage to kill the Beast and defeat the Berserks.