Skullcrusher is a Rumblehorn who is Stoick's new Dragon and later Eret's, in How To Train Your Dragon 2.
In comparison to Grump, Skullcrusher is stern and serious looking, and sometimes a little stubborn, (corresponding with the personality of Stoick). He looks like a cross between a dragon, a Triceratops and a beetle (due to his neck plates).
It is currently unknown when Stoick acquired Skullcrusher, save that it must have been since Stoick released Thornado. Despite this, the two are shown to be close, with Stoick being comfortable riding Skullcrusher alongside Grump and Gobber.
Following Stoick's death, Hiccup suggests that Skullcrusher pass into the care of their new ally and former dragon-trapper Eret, recognizing Eret's skill and courage in helping Berk defeat Drago Bludvist.