

Skullcrusher is a Rumblehorn that appeared in HTTYD 2 and is Stoick's dragon until his death, becoming Eret's later on.
How Skullcrusher met Stoick is unknown, since it was not shown how the viking met the dragon but it must have been after the relase of Thornado in the TV series. Stoick and Skullcrusher are shown to be close, with the dragon's personality being similar to his rider's. After the death of Stoick, Hiccup suggests Eret to take care of Skullcrusher, with the dragon accepting the boy as his new rider. In the end of the movie, the two are shown to enter the Dragon Race with the oter riders in the back of Skullcrusher, perfectly comfortable about riding him.