Rumblehorn

The Rumblehorn is a Tracker Class dragon that appeared in the movie How To Train Your Dragon 2 and the third season of the Dreamworks Dragons TV show.

Dragon Appearance
The Rumblehorn has relatively large wings, a wide torso, and a tail with a club-like hammer on the tip. Its most notable feature is the heavily armed front half of its body with firm armor plates on the neck and a large lower jaw, a battle axe-shaped muzzle, which is always digging in the dirt, looking for scents, and two, very sharp, elongated horns resembling those of ceratopsian dinosaurs, but lacking a beak. The Rumblehorn has a very acute sense of smell, and is determined to track down and find anything once it has picked up the scent. In total, they look like a mix of truffle pig, a rhinoceros, a battle axe, and a scarab beetle.

Abilities and Weaponry
It can shoot long-ranged fire "missiles" from its mouth which initially starts out as a white-hot fireball that quickly solidifies and turns to a warmer color before it ends up in a sooty, stony material when it hits its target.

Being a Tracker Class dragon, their powerful sense of smell makes them able to find any Viking scent from long distances even if the material that worn from the water for certain period of time. They can find anything, based on scent alone.

Rumblehorns are extremely strong dragons, for they are able to carry large Vikings and their weapons, as well as ramming down a sea stack while flying in full speed.

Their physical weaponry are having a powerful long tail that can be used as a club with spikes, sharp long horns and sharp teeth.

Rumblehorns appear to be extremely intelligent, hiding from their enemies in bushes and creating traps with their footprints. They have also been shown to attempt to chase Hiccup and the gang off Dragon's Edge by pretending to harm them, other native dragons and destroying buildings. They have even outsmarted Hiccup and the gang numerous times.

Behavior
Rumblehorns always have their snouts to the ground, sniffing around for something edible. They can be aggressive, but are also friendly towards their riders. Their food of choice is unknown, but they are probably carnivorous. They are also highly intelligent and determined. They run like rhinoceroses. As shown by the still wild Skullcrusher, Rumblehorns can be very caring and protective of those in danger, as seen when Skullcrusher tried to warn everyone of a tidal wave heading towards Dragon's Edge.

Known Rumblehorns

 * Skullcrusher
 * Seedling Rumblehorn

How to Train Your Dragon 2
A Rumblehorn known as Skullcrusher, is introduced as Stoick's new dragon. He is helped to track Hiccup down and become Eret's dragon after Stoick passed away.

Race to the Edge
In the episode Crushing It, Hiccup and the gang face a strange new dragon that has been targeting native dragons and destroying Dragon's Edge. Hiccup named it the Rumblehorn. They get Gobber to build a fortress, but to no avail. Eventually, Hiccup allows his father to help them get rid of the rouge RUmblehorn but it always outsmarts them. Back at the Edge, it attempted to attack Gobber and Toothless was told to shoot him down. Sensing that something was not right, Stoick tamed the Rumblehorn and brought the gang to the sea. Hiccup then realised that a large wave strong enough to destroy the Edge was heading their way and the RUmblehorn was trying to chase them away from the island in order to save them. Eventually, they worked together to surround the island with Gobber;s fortress and the Rumblehorn, together with Stoick, collapsed a sea stack just in time to stop the wave. Stoick then keeps the Rumblehorn as Thornado's replacement and calls it Skullcrusher.

Titan Wing
Source: Dragons: Rise of Berk

Titan Rumblehorns appear to have developed a shiny green armour. There are more plates to their armour and it appears harder. The horns on their head are sharper and longer, and their wings are cyan in colour. Furthermore, their tail has grown more spikey tips.

Trivia

 * A Rumblehorn named Skullcrusher is the new dragon of Stoick the Vast in the second film and later Eret at the end of the second movie
 * The Rumblehorn shares a similar body structure with the Triceratops.
 * Its lower jaw seems to have been originally able to go two ways, as evidenced by a piece of concept art.
 * The Rumblehorn also appears in the game School of Dragons.
 * The Seedling Rumblehorn slightly resembles a tortoise.