Grim Gnasher

The Grim Gnasher is a medium-sized Sharp Class dragon that first appeared in Dragons: Race to the Edge.

Official Description
"Despite their small size, Grim Gnashers love nothing more than to sink their thousands of teeth into smaller and weaker dragons. Sneaky and opportunistic, Grim Gnashers circle above their injured prey like carrion birds. Even though they hunt in packs, Grim Gnashers prefer to feast on a dragon that can't defend itself, rather than take on a healthy dragon. Yet Grim Gnashers are just as deadly with their long-range attacks. Possessing a shark-like ability to regenerate row after row of sharp teeth, these dragons spit out fiery blasts of fangs with remarkable precision and accuracy. But perhaps the most dangerous thing about Grim Gnashers is their ability to plan and communicate with each other to outsmart their quarry."

- Dragonpedia

"These Sharp Class dragons live off the dragons which arrive on Vanaheim. Using their unique ability to blast razor-sharp darts made of their teeth, Grim Gnashers hunt down sick dragons and the Sentinels who protect this sacred island. While not the friendliest of dragons, Grim Gnashers live in packs and work well with others. The alpha of the group is easy to spot by its red wings and stripes, as opposed to the regular Grim Gnashers’ purple hue."

- School of Dragons Website

Egg
The Grim Gnasher egg in School of Dragons is oval and has a dark color. It has scale-like patterns that are red, yellow and pale pink. It is covered in spikes, for defense purposes.

Hatchling to Adult
Grim Gnashers resemble Grapple Grounders as they have similar long, serpentine bodies albeit thicker, a small head and four legs. They have three main sets of horns on their heads, complemented by more along their necks and backs. In addition, they have a long nasal horn and a distinct under-bite with small rows of pointy teeth, giving them a sinister appearance. Covered with prominent, iridescent purple scales, they have a paler underbelly but more vibrant coloration on their backs and wings.

The leader Grim Gnasher has purple scales, red stripes on its back and red wings, differentiating itself from the rest of the group.

Titan Wing
Titan Wing Grim Gnashers, as revealed in School of Dragons, have similar coloration patterns as the Broad Wing stage — a solid base color with another color along the back. Titan Wing Grim Gnashers have the same body structure as adults but sport larger and thicker spikes and horns. The largest pair of horns on the head is reminiscent of those of a longhorn cow or other bovine.

Regenerating Teeth
Much like sharks, Gnashers have the ability to shed and regenerate as many rows of teeth in their lifetime. They are said to have a thousand teeth. Furthermore, they can attack by shooting them in their blasts with incredible precision.

Teamwork and Communication
Their remarkable communication skills are the core of their extraordinary teamwork. They are able to plan and communicate to plot against their prey. As such, they tend to hunt in packs and ambush their prey. Similar to the Speed Stingers, the Grim Gnashers have a leader (or an alpha) whose orders they follow.

Speed and Agility
Grim Gnashers are very fast and agile dragons that are able to swiftly ambush their prey as well as evading attacks.

Behavior and Personality
Grim Gnashers are scheming and cunning predators that tend to plot against their prey. Furthermore, they exploit the weaknesses of the old and sick dragons of Vanaheim, a divine funeral ground for dragons to spend their last days. This behavior is likened to that of a vulture who circle weak prey and consume carrion. As Sentinels guard Vanaheim and both the dead and dying dragons, Grim Gnashers have become their enemies since they are taking advantage of a ready food source.

While the Grim Gnashers appear to be villainized, in a functioning ecosystem, these dragons are an important part of removing weak animals and, presumably, cleaning up carrion, allowing the food cycle to continue, just as real-life scavengers do.

Grim Gnashers work in packs like other creatures such as wolves. There is a pack leader or alpha, who has a red back and wings to distinguish it from other pack mates.

Season 5
Grim Gnashers are introduced in the episode, "Searching for Oswald... and Chicken". Hiccup and Fishlegs return to Vanaheim, along with Dagur, following up on clues from Oswald's Diary. They encounter the Grim Gnashers there, a predatory dragon-eating species preying on the weak and dying dragons on the island. They also find out that Oswald had made it his mission to assist the Sentinels protecting the ailing dragons from these predators. There was also a diagram of a Grim Gnasher on a wall in Oswald's hut in Vanaheim.

Season 6
Grim Gnashers return in “Guardians of Vanaheim”, not long after Dragon Flyers attacked and incapacitated the Sentinels. The Grim Gnashers make their presence clear after they seemingly kill and devour a Flyer that has been captured by the Dragon Riders while trying to escape with a Dragon Eye lens. The Grim Gnashers then make their move towards the hibernating Sentinels when Tuffnut, Ruffnut, Barf and Belch start attacking them. Knowing that the Sentinels are the only ones powerful enough to stop the Grim Gnashers, Fishlegs and the Twins have their dragons arouse the guardian dragons by exposing them to the heat of their fire. The plan worked as the Sentinels awaken and drive off the Grim Gnashers once again.

School of Dragons
Grim Gnashers were released in this game in March 2018 as part of the "Wrath of Stormheart" Expansion, as NPCs (non-playable characters). All individuals seen are purple in color, with red backs. They attack the player and Dragon Riders on Vanaheim and appear as opponents in some of the levels of the 'Dragon Tactics' activity. Some Grim Gnashers appear to be under the control of Nikora Stormheart, though it is not explicitly discussed.

In April 2018, the Grim Gnasher was released as a dragon players could train and ride.

Later in June 2018, School of Dragons released a titan form of the Grim Gnasher, the first to appear in the Franchise.

Trivia

 * The Grim Gnashers' ability to shoot their teeth is possibly inspired by those of the Poison Darters or Razorwings from the How to Train Your Dragon Book series.
 * Since Grim Gnashers prey on sick and dying dragons and Sentinels protect them, it is possible that the two species are natural enemies.
 * The Grim Gnasher's ability to regenerate its teeth may be based off that of a shark's.
 * The Grim Gnasher's running animation in School of Dragons greatly resembles a horse's running.