Rumblehorns shoot long-ranged fire missiles which explode on impact. They can find anything on scent for miles away, even with just a weak scent from a helmet.
One of the Rumblehorns, Skullcrusher, belonged to the previous chief of Berk, Stoick the Vast, who was the father of Hiccup, and also the husband of Valka. But when Stoick died, due to getting shot by Toothless' blast, Skullcrusher then belonged to the once dragon trapper Eret son of Eret. Rumbelhornes are very tough and can destroy almost anything. They are very intelligent and loyal. They may look scary but they are very kind and sweet.