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. Extremely dangerous, kill on sight."

- 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

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. Interestingly, they are laid in very cold climates on ice. Bork the Bold is seen stomping unsuccessfully on one, on what appears to be a glacier.

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. Its head somewhat resembles that of an angler fish. Several other dragons share similar head shapes such as the Skrill and the Flightmare. Its wings look similar to those of a Changewing. 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 Stoick (excluding the tail), but in How to Train Your Dragon 2, it is much bigger (if you look at these Thunderdrums from the side, the mouth are the same length as Toothless' entire body, including his tail).

According to the Dragon Manual, a Thunderdrum is roughly the same size as an adult Viking, though they are clearly far larger. All Thunderdrums seen in adaptations before How to Train Your Dragon 2 are not much larger than medium or large-sized dragons, though their tails are very long. Baby Thunderdrums only 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
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. They have developed a larger talon on the edge of their wings. 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 (according to Rise of Berk).

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 temporally 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 temporally). By combining roars of several individuals, the roars are able to knock away several large dragons at mid-distance and instantly and literally blow them off.

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.

They are also considered to be one of the most omnipotent and powerful of all dragons in terms of orbit. These marine dragons are capable of flattening their bodies by expelling oxygen from lungs for a limited period of time and enhance underwater mobility from to skim on water surfaces to dive deeper for feeding. They are also able to fly at really high altitudes.

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 among the most powerful dragons, as was confirmed by both Hiccup and Stoick. 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 even 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'. Although Stoick is only 350 lbs.

Agility and 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
The Thunderdrum has one of the most powerful blasts of all dragons, however, their blast 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. (Though Thornado was seen to respond to his name when Stoick wasn't yelling.)

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. An advantage of being nearly deaf includes immunity to the Death Song's song, which makes Thunderdrums able to escape capture by the Death Song and fight it effectively.

Speed
It's 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.

Behavior and Personality
They form pods in a hunt or on migration, and take care of each other and can be compassionate, and these features are similar to those of cetaceans. The Scauldrons also share at least the first of these traits (most so far encountered specimens had not been calm at times), and both of them are whale-like dragons. This dragon is reclusive in nature, living in sea caves and dark tide pools or even 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. 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.

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 exclusive 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 train it. However, when they bring it back to the academy and put a muzzle on it to keep it from using its roar on This dragon is picked for its ferociousness by Stoick the dragon becomes too stubborn and eventually breaks free.

After finding 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, and appeared as Stoick's dragon ever since.

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 its 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. They nearly destroy the village, and Stoick orders them away. When they abandon the babies on an island, wild dragons instantly approach them. The babies, vulnerable and weak, are no more than easy prey. Hiccup and Stoick immediately rush to defend the babies. After defeating them, they realize that the babies cannot care for themselves in the wild. Stoick, with much grief yet joy, free Thornado 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, though Tuffnut pointed out that the Thunderdrums couldn't hear him.

How to Train Your Dragon 2
A herd 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.

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 Thunderdrum, and Tectonic Thunderdrum, and hybrids appear in this game.

Trivia

 * Thunderdrums seem to resemble Eagle Rays in shape and color. Like Spotted Eagle Rays, 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 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 it's overall power is 73, they have proven to be extremely strong. Thornado carries Stoick on his back while pulling 2 ships out of their harbor and at another time carries Stoick and Gobber without showing any signs of struggling. 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 Sequel.
 * 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.
 * The Thunderdrum, Night Fury, Sand Wraith, Singetail, and the Stormcutter are the only dragons so far that have 4 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 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.
 * In the 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.