<P> The first book in the series , following Hiccup as he captures a dragon as a rite of passage and attempts to train him so that he will not be exiled from Berk , as its tradition . Led by Gobber the Belch , Hiccup manages to catch a small dragon , whom he names Toothless , and attempts to train it through his own methods , when the How To Train Your Dragon book was found to have only one page and therefore unhelpful . During the final part of the rite of passage Toothless offends another dragon and a fight ensues between all the dragons . As this is seen as failure to train the dragons correctly , the boys are exiled , allowed to stay one night while a storm rages . During the storm , three Sea Dragons are washed up on the shore of the island and one seems a threat to the Vikings . Hiccup is chosen to negotiate with the dragon , who has eaten one of the other dragons . However , the dragon , who calls himself the Green Death , says he is going to kill all the Vikings . While the village elders argue over how to attack the Green Death , Hiccup , the boys and their dragons start a fight between the Green Death and the other sea dragon , the Purple Death , resulting in Hiccup nearly being swallowed and having to be rescued by Toothless , killing both sea dragons in the process . Hiccup and Toothless become heroes because of their bravery . </P>
what kind of dragon is at the end of how to train your dragon
sea dragon