Thunderdrum

"Thunderdrum. This reclusive dragon inhabits sea caves and dark tide pools. When startled, the Thunderdrum will produce a concussive sound wave that can kill a man at close range."

- Hiccup as he reads through the Dragon Manual

The Thunderdrum is a large Tidal Class dragon that was first mentioned in How to Train Your Dragon and first appeared in Book of Dragons.

Official Description
"Instead of breathing fire, the Thunderdrum produces a strong, concussive sound that can kill a human at close range. The blast is so powerful that the dragon is said to "get its power from Thor himself". Legend also has it that when the Thunderdrum hatches from its egg, it makes a sound so loud it rattles the sky. When not swelling its body up to yell, Thunderdrums can actually flatten their body by expelling all oxygen from their massive lungs for a limited period of time. In this sleeker state, Thunderdrums can better skim the ocean surface or even dive beneath the waves in search of prey. While it's true that Thunderdrums create tremendous amounts of noise, they also possess the ability to cancel out each other's sonic blasts. By modulating its roars to the proper frequency, a Thunderdrum can use its soundwaves to negate an attacking Thunderdrum's bellow, rendering it into a rather calming wave of white noise."

"At home on land or sea, this Tidal Class big mouth has a Sonic Blast strong enough to kill a Viking . . . or at least soil his britches. The Thunderdrum holds a steady course in a fight while it blasts opponents with a sonic boom."

- Dragons: Rise of Berk

"Classified as members of the Tidal Class, Thunderdrums are large dragons that can thrive in land or sea. They are known for their massive mouths that generate sonic blasts strong enough to stun a human at close range. For this reason, Thunderdrums are believed to derive their power from Thor himself. Because of their sonic blasts, Thunderdrums tend to be nearly deaf, making them immune to the Death Song’s call. They can fly at extremely high altitudes. Along with their incredible strength, they also possess a prehensile tail that is strong enough to carry heavy items. They can breathe fire too, but this takes a lot of energy out of them and is not their preferred method of attack. What is also fascinating about the Thunderdrum is how it swims through the water. It has the ability to expel air from its lungs to flatten its body. This makes it easier for a Thunderdrum to skim along the surface of the water, or to dive deep down to hunt for food. These dragons may be strong-willed and intimidating, but with a dedicated trainer that is just as stubborn, the Thunderdrum can become a loyal friend."

- School of Dragons Website

"Thunderdrum is capable of delivering a thunderous sonic blast that can be heard for miles. The winds which accompany the blast can even snuff out a rival dragon's fire."

- DreamWorks Dragons: Wild Skies

Egg
In School of Dragons, the eggs have electricity running through the eggs. The egg's core is glowing while the exterior is of a lighter shade of blue.

In Dragons: Rise of Berk, the egg comes in various colors. They have a slightly more pointy top. Faint specks can be found in its middle and it appears to be rather shiny.

In the Movie Short, Book of Dragons, Thunderdrum eggs appears to be a base color of aqua, with lime green speckling.

Hatchling to Adult
This dragon relies mostly on its two sets of wings, one primary and one smaller set to the rear, using them to get around and move through the water like a tornado.

These dragons have stubby legs and long, skinny tails. It also has a series of backward facing spikes sticking out of its back. The Thunderdrum's body resembles several marine creatures such as a basking shark, a whale shark, a manta ray, or a baleen whale. According to the Dragon Manual, Thunderdrums have really powerful wings and the spikes on their tails are very sharp.

In Dragons: Riders of Berk, this dragon is just bigger than a Gronckle (excluding the tail), but in How to Train Your Dragon 2, it is much bigger.

All Thunderdrums seen in adaptations before How to Train Your Dragon 2 are not much larger than medium or large-sized dragons. Baby Thunderdrums grow up to 11 inches tall.

In How to Train Your Dragon 2, much larger Thunderdrums are seen. These Thunderdrums are longer than Blue Whales and their wingspan is long enough for Toothless to fly under one that was jumping out of the water. The maximum size for these dragons is unknown. Thunderdrums in this size are probably too expensive to animate, so they are smaller in the Series.

Titan Wing
In Dragons: Riders of Berk, Titan Wing Thunderdrums are larger than normal adults ones. They have three main colors on their body: blue, turquoise, and purple. Their wings have these three colors and many white specks. The talons on the edge of their wings grow larger. Their body is mainly blue in color. These Titans possess lots of sharp teeth and a long ledge, with its nostrils, on the top of its snout. Their second set of wings is larger and they have a row of spines along their tail and spikes all over their back.

Abilities
Like nearly all dragons in the Manual, they are classified "extremely dangerous, kill on sight." Thunderdrums are experts in producing sound and have many of unique abilities related to sound waves.

Babies
It is also said that when a Thunderdrum hatches from its egg, it makes a sound so loud it rattles the sky. Baby Thunderdrums have the strength to be able to drag two young Vikings on its tail with no sign of struggle. As hatchlings, their thunderous roar is powerful enough to send heavy Vikings to the air and can destroy some large objects such as Hiccup's invention, the Thunder Ear.

Sonic Blast and Fire Blast
The name comes from its main mode of attack/defense. The Thunderdrum produces a strong concussive sound that can kill a human at close range. It is not only capable of temporarily stunning other dragons but also can even extinguish flames shot by other dragons. The blast is so powerful that the creature is said to "get its power from Thor himself." Only the Screaming Death has a tolerance with this attack (able to stun it temporarily). By combining roars of several individuals, the roars are able to knock away several large dragons at mid-distance.

Like its sound wave booms, a Thunderdrum can shoot blue blasts of fire that get bigger the farther they go. And these fire blasts also travel at the speed of sound. The downside to this power is that it takes a lot out of a Thunderdrum to employ it, so it's not often used.

Thunderdrums can blast waves of blue fire if necessary, but this uses a lot of energy.

In order to protect themselves from their own sound emissions, the Thunderdrums developed a system to offset sonic blasts by regulating wave frequencies of blasts to neutralize others' roars.

Strength and Combat
Thunderdrums are some of the most powerful dragons. Thunderdrums are also some of the all-around most useful dragons as they can dive down to the depths of the ocean and fly at extremely high altitudes.

Thunderdrums have been seen defeating wild dragons, pull two ships at the time with the added weight of Stoick the Vast, defeating a whole herd of wild boars and a wild specimen has been seen destroying a row of sea stacks by flying through them.

Endurance and Stamina
Their endurance and stamina are very impressive as shown by Thornado, who was able to take attacks from Stoick and still fly in great speed. Despite Hiccup referring to Stoick as a '400 lb man', the latter is only 350 lbs.

Prehensile Tail
They also have been shown to be quite flexible, as Thornado managed to grab Stoick with his prehensile tail able to pulled him underwater and slapped away several wild boars in battle.

Immunity to the Death Song
A Thunderdrum bellow is so loud that Thunderdrums tend to be almost deaf, making it the only known dragon which is immune to the Death Song's call.

This modulating also prevents sounds from damaging surroundings ("rendering it into a rather calming wave of white noise!"). Because of this, Thunderdrums are nearly deaf. The School of Dragons claims that like snakes they have no outer ear so they are virtually deaf out of water, but they can hear very well underwater like whales and dolphins.

Speed and Agility
Thunderdrums are able to fly at great speeds in the air, and swim through water like a tornado.

Flattening their bodies allows them to skim through the water at even greater speeds or allow for deeper dives for feeding.

Behavior and Personality
They form pods in a hunt or on migration, a feature similar to those of cetaceans. Generally reclusive in nature when alone, living in sea caves and dark tide pools or in open waters.

Understandably, they are strident and assertive, the loud Thunderdrum always makes its feelings known.

Adolescents are shown to be mischievous to Vikings and dragons alike as they can be very annoying to them. Since they don't stop roaring or mimicking other sounds. However, the adolescents will acquiesce to any adult of the same species, regardless of relationship or lack thereof.

Thunderdrums are so stubborn that they can be tough to train. Thunderdrums show a real parental instinct to any young, even if it's not their own.

According to Hiccup in Race to the Edge, Thunderdrums have a habit of holding grudges against their enemies.

Training
Training a Thunderdrum, especially as an adult is a challenge as Thunderdrums are almost deaf. Showing protection and gaining the Thunderdrum's trust is an easier way to train it, as seen by Stoick and Thornado. Adolescents also don't or can't listen except to mature adults. It is easier to train one from birth or have an adult to help. However, adults can be very protective of their young, regardless of their offspring's' ill-behavior, as seen with Thornado when trying to watch over Bing, Bam, and Boom. These dragons give in easier during times of crisis, as displayed when Thornado had to save Whirlwing, or when Earsplitter had to save his child.

Dragons: Titan Uprising points out that because of their deafness, many Thunderdrums respond best to visual cues during training, especially Reef Thunderdrums.

How to Train Your Dragon
The Thunderdrum is one of the dragons Hiccup reads about in the Dragon Manual, while searching for information about Night Furies. Like all dragons, it's classified as an extremely dangerous creature that needs to be killed on sight.

Book of Dragons
The Thunderdrum first appears in this short. It is classified into the Tidal Class in the Dragon Manual and some of its features and abilities are reavealed. Gobber tells the story of how Bork the Bold once found the nest of a Thunderdrum in a cold region. However, he didn't know that Thunderdrum eggs hatch with an explosive sound that rattles the sky, and he found this out the hard way.

Dragons: Riders of Berk
In "How to Pick Your Dragon", the Thunderdrum was first labeled as a rogue dragon attacking Berk's fishermen out at sea. While Hiccup tries to find Stoick a dragon so he can help his village more effectively, the rogue dragon strikes again. When they arrive on the scene, Stoick is satisfied with the beast and requests his son to help him train it. However, when they bring it back to the academy and put a muzzle on it to keep it from using its roar, Stoick brawls with it, causing it to escape.

After locating it, Stoick and Hiccup learn that it was accompanied by Whirlwing, another Thunderdrum that was injured, which is why it attacked the fishermen, so it could get food for its friend. Hiccup leaves to fetch the others while Stoick stays behind with the Thunderdrums, but they are soon ambushed by wild boars. Stoick finally bonds with the dragon and together they defeat the boars. He was eventually named Thornado by Stoick.

Dragons: Defenders of Berk
In "Bing! Bam! Boom!", Hiccup and Stoick find three baby Thunderdrums on a sea stack. Puzzled why they were left there, the duo decided not to probe into the matter and left. The babies gave chase, but Thornado warded them off with his sonic blast. Hiccup, after convincing his father, brings them back to Berk to train and they were named Bing, Bam, and Boom. They prove to be too mischievous and stubborn to be trained and only listens to Thornado. Nearly destroying the village, Stoick orders them away. When they abandon the babies on an island, wild dragons instantly approach them, viewing them as easy prey. Realizing that the babies cannot care for themselves in the wild. Stoick bittersweetly sets Thornado free to care for the trio.

Season 1
With most of their dragons mysteriously gone on Melody Island in "Imperfect Harmony", the gang sets off to find them, stumbling upon a wild Thunderdrum. After hitting them with his sonic blast, he was chased off by Hiccup and Toothless. Hiccup ran into him again while trying to escape the Death Song. While the Thunderdrum was mad at Hiccup about before, he focused more on fighting the Death Song. They managed to escape and Hiccup trained him to help save the others as the Thunderdrum was immune to the Death Song's call. After breaking the dragons and Riders out of the amber cocoons, Hiccup realized the reason why the Thunderdrum was fighting the Death Song was that it had captured his son. Hiccup and Toothless lured the Death Song into a cave and the Thunderdrum blasted it shut after the duo made it out. The Thunderdrum happily reunited with his son and Hiccup recommended the two find a new home.

Season 6
Several wild Thunderdrums were summoned by the Berserker Bewilderbeast during the final fight against the Dragon Hunters and Flyers in "King of Dragons, Part 2".

How to Train Your Dragon 2
A pod of gigantic Thunderdrums was seen in the beginning of the movie, swimming at the surface of the open ocean while Hiccup and Toothless were flying past them.

The Ice Castle
During his Dragon Auction, Dammen mentions that he has Thunderdrum eggs for sale.

The Stowaway
A wild Thunderdrum gets into a fight with Stormfly over food, creating chaos in the village of Berk. Fortunately, Hiccup manages to stop the fight by giving both dragons food at the same time.

When Hroar goes to Dragon Island in order to enrage many dragons and lead them to Berk, he does so with several Thunderdrums. However, after he is thrown off his saddle, the Thunderdrums and all the other dragons return to their island.

The Legend of Ragnarok
When Hiccup and Astrid go out at the sea, they spot an agitated Thunderdrum and a Scauldron jumping off the water.

The Serpent's Heir
Several Thuderdrums appear along with other Tidal Class dragons that offer tribute to Toothless, their new Alpha.

How to Train Your Dragon: The Hidden World - The Movie Storybook
A Thunderdrum was briefly seen being ridden by a Berkian in this book, following the Alpha Dragon Toothless on a quest for the Hidden World.

DreamWorks Dragons: Wild Skies
In the game, Thunderdrum can be tamed. It lives in Wrecker's Reef, and one must feed it crabs or fish in order to tame it. You will need 10 Gold and buy a Crab Net, then go to Wrecker's Reef, where you then select the crabs. The Thunderdrum is a Tidal Class dragon, and it can release a sonic boom. When the player rides it, the dragon's mouth is closed. When you press the space bar, it will open its mouth and screech at the target. Other Vikings will say that the player is as strong as Stoick after having tamed it.

Dragons: Rise of Berk
The Thunderdrum, along with its Titan form, became available in Rise of Berk. Bing, Bam Boom, Earsplitter, Lil Lullaby, Whirlwing, and Thornado also appeared in it.

School of Dragons
The Thunderdrum is also seen in School of Dragons. Only members can own a Thunderdrum for free in the first pick. Stoick's Thunderdrum, Thornado, appears in the quest 'The Sickly Dragon' where Thornado is seen sick and you have to find mint leaves in the wilderness which is made into tea.

Dragons: Titan Uprising
Several Thunderdrum individuals, like Warcry, Waveshaker, Reef Thunderdrums, Tectonic Thunderdrums, and the Shifty Murklurker, and hybrids appear in this game.

Trivia

 * Asterisk-Transparent.png Due to the size differences seen among the Thunderdrums throughout the franchise, there may be 'average'-sized Thunderdrums using the official stats given by DreamWorks, and there may be larger-sized Thunderdrums. Those seen in How to Train Your Dragon 2 are calculated to be over 150 feet (45.72 meters) long. This is based on a series of size comparisons with Toothless, as he was seen to easily fit under a Thunderdrum's wing. These size comparisons had a wide span of results, ranging from 38 meters (125 feet) up to 46 meters (151 feet). In particular, the Thunderdrum that jumped over Toothless had the most fitting size of 46 meters.
 * Thunderdrums seem to resemble spotted eagle rays in shape and color. Like said species, they are blue with white spots and "fly" through water with wings (Thunderdrums also have a slight resemblance to whale sharks; as they have similar gaping mouths). They also seem to resemble the Giant Bee-Eaters from the books.
 * The design of the Thunderdrums seems to be based on sharks or baleen whales, as it has whale shark spots, basking shark mouth, and has a shape of a spotted eagle ray (which is a relative of the shark). Its torso could possibly be based on ridges on rorquals' belly that dramatically expand when they feed. Additionally, Thunderdrums' humming sounds similar to baleen whales' singing.
 * The Thunderdrum's ability to produce a powerful sonic sound could be based on echolocation and sonic sounds used by cetaceans, especially that of baleen or sperm whales that can reach several thousand kilometers away and are capable of paralyzing large prey such as giant squids.
 * The Thunderdrum was the first new dragon that was introduced in Book of Dragons to appear in DreamWorks Dragons: The Series.
 * In Book of Dragons, there is a school of Thunderdrums, while lone Thunderdrums have also appeared in the rest of the franchise. This trait of schooling and living alone may be based on the hammerhead shark, as some socialize in schools to mate and migrate and some hunt alone.
 * Though its overall power is 73, they have proven to be extremely strong. Thornado carries Stoick the Vast on his back while pulling two ships out of their harbor and at another time carries the latter and Gobber the Belch without showing any signs of struggle. Also, Stoick beats up a Monstrous Nightmare, one of the toughest dragons known, in a few seconds, while it took him nearly a minute just to hold Thornado steady.
 * Thornado and the other Thunderdrums that appear in the show are much smaller than the ones in How to Train Your Dragon 2.
 * It is possible that a Thunderdrum's growth slows down if they are out of water for a prolonged time.
 * In "King of Dragons, Part 2", Thornado, Bing, Bam, and Boom are about the same size as to how they were seen in their last appearance, which took place at least 3 years ago. Torch, Garffiljorg, and the New Protector grew to full size within only a few months. It is possible that the growth rate of Thunderdrums is much slower than that of other dragon species.
 * If this is true, then Thunderdrums may have extraordinarily long lifespans, given how these dragons are gigantic in the How to Train Your Dragon 2.
 * Another reason could be that the Thunderdrums in How to Train Your Dragon 2 were fully grown, and Thornado and the ones in the show are still adolescents.
 * Another possibility is that Thunderdrums present sexual dimorphism and females are considerably larger than males.
 * Yet another possibility is that its a production goof.
 * The Thunderdrum, Night Fury, Sand Wraith, Singetail, and the Stormcutter are the only dragons so far that have four wings (though out of these dragons, the Night Fury's and Sand Wraith's secondary wings are not fully functional).
 * Even though it has been stated that the Thunderdrum's sonic blast could kill a man at close range, the teens and Stoick only get minimal damage or are just blasted away when Thornado, Bing, Bam, or Boom use their sonic blast. The Dragon Riders are also not affected when four of them use a combined sonic blast.
 * The roar of the Thunderdrum resembles the sound of a TIE fighter from Star Wars.
 * It is possible that Thunderdrums can grow based on their habitat. For example, if a Thunderdrum lives on a reef, it might not grow as big as one out in the open ocean.
 * It is possible that Thunderdrums hear infrasound better rather than normal sounds. And its possible that like bats, Thunderdrums can plug up their ears with special muscles that prevent it from being deafened by its own roars.
 * In the Dragons: Rise of Berk battle mode and brawl mode, the Thunderdrum doesn't expand its body, but only opens the mouth when firing the sonic blast.
 * It is possible that Thunderdrums can move much faster than a speed stat of 14, as proven by Earsplitter, who was able to evade from the Death Song which has a speed stat of 17.