As Twyin Lannister once said on Game of Thrones, Aegon the Conqueror and his dragons “changed the rules” of warfare. Before Aegon Targaryen landed on the eastern shores of Westeros with his two sister-wives and their three dragons, the realm was made up of independent kingdoms. Thanks, thanks to his dragons it wasn’t long before Aegon made his enemies bend the knee, or burn in a bath of dragonflame.

Almost three hundred years after Aegon conquered the Seven Kingdoms on the back of his dragon Balerion the Black Dread, another Targaryen rode her dragon to Westeros and destroyed many Lannister forces in a field of fire.

Daenerys Targaryen, the first person to hatch dragons in nearly 150 years, hopes to use them to take the Iron Throne. It is the seat where the blood of the dragon ruled a new kingdom, forged by Aegon in Balerion's flames.

While dragons are the greatest tool of warfare that Westeros has ever known, they are as hard to control as they are massive. Dragons have a long, mysterious  history that goes far beyond the Narrow Sea. They are complicated, intelligent creatures, who share unspoken bonds with the few lucky enough to call themselves dragonriders.

So, as Daenerys gets ready to unleash the full fury of her children against her enemies in the Seven Kingdoms the same way Aegon once did, here are the 16 Things You Need To Know About Dragons On Game Of Thrones.

Dragons never stop growing

Aegon’s dragon, Balerion the Black Dread, never stopped growing, and by the end of his life they say his jaw was big enough that he could eat an entire mammoth. His teeth were strong enough to do it too, since they were as big as swords.

Balerion’s wingspan was wide enough that a whole city would be in shadow when he passed over. For some perspective of how big that would be, prior to season seven, Game of Thrones’ co-creators said that Daenerys’ dragons are now the size of jumbo 747 airplanes.

However, dragons will only grow if given enough food and freedom of movement. When the Targaryens started keeping them in the Dragonpit of King’s Landing, they started getting smaller. This is partly why Tyrion freed Rhaegal and Viserion from their confinement in Meereen.

A dragon must be given room to grow, because, once they are freed, they will never stop growing bigger and bigger.

The oldest dragon died at 200 years old

Balerion was able to grow into the largest dragon in the history of Westeros because he also lived the longest life, dying at over 200 years of age. At the time of Aegon’s landing, he was thought to be close to 125 years old, and he died 94 years after Aegon was crowned king of the Seven Kingdoms.

He lived such a long life that he was actually born in Valyria, and was one of the five dragons brought to Dragonstone by Lord Aenar Targaryen. Aenar’s daughter had a prophetic dream about the destruction of Valyria 12 years before the Doom that destroyed it.

This was why Aenar fled, but Baelerion was the only dragon of the five to live long after. Two other Targaryen kings would ride on the back of Balerion after Aegon’s death.

Daenerys’s dragon Drogon, who some think is Balerion reborn, might be huge now, but he is still just a newborn compared to how long he might live.

Some believe dragons are tied to magic and the seasons

The last dragon died almost 150 years before Daenerys emerged from the ashes with her three children. During this time period, it is said that magic in the world grew weaker, and that the uneven seasons were made up of shorter summers and much longer and colder winters.

Whether or not dragons truly are tied to magic and the seasons is unclear, but in one of the novels, a pyromancer of the Alchemist’s Guild told Tyrion Lannister that their production of wildfire was suddenly as good as it was when dragons were alive.

He gave credit for the uptick and speed of their manufacturing to their magical spells working better, unaware that dragons had come back to the world in Essos.

Dragons themselves have many magical characteristics, thus their presence might account for increased magic in the world.

Their scales thicken and grow harder with age

Despite their enormous size, dragons are not indestructible (as we have seen), but they do get more difficult to injure as they age. This is due to their protective scales, which get stronger and harder over the years, offering greater protection to the muscles and flesh.

While these thicker scales aren’t guaranteed protection against fire, they are nearly impervious to flame. This helps on the rare occasions when a dragon fights another dragon.

Dragons don’t need to wear protective armor because they naturally have their own coat. Combined with the strength of their bones, which is said to be lighter and more flexible than steel but just as strong (and completely immune to fire), they are an unparalleled challenge for any army to bring down.

An archer would want to aim for their eyes, or possibly their wings. However, dragon wings themselves are akin to leather, a material often used as protective armor among soldiers. So, while men get weaker and more vulnerable with age, thickened scales make older dragons far harder to defeat.

Their flame can melt steel and stone

Similar to their scales, the intensity of a dragon's flame gets hotter as a dragon gets older. Not only can the oldest dragons melt steel, they can even melt stone.

The incredible heat of dragonflame made it possible for the Valyrians to build unmatched monuments. The oldest Valyrian outpost, Volantis, has huge, thick 200-foot seamlessly high walls known as the Black Walls.

The Black walls form a massive, fused black oval, which is thick enough to have six chariots run side-by-side on the top of it. Yet there isn't a seam within it thanks to the dragonflame that forged it.

Aegon also used Baelerion’s dragonflame to forge the Iron Throne, and the lost art of making Valyrian steel is believed to have included forging it in dragonflame.

Daenerys used Drogon to turn men wearing suits of armor into ash, and yet dragonflame can be so hot that it can build cities rather than just destroy them.

Their bodies give off a tremendous amount of heat

It is said that dragons are “fire made flesh,” which is why the followers of R’hllor believe them to be the living embodiment of the Lord of Light. However, “fire made flesh” is not just a metaphorical expression, nor is it just a reference to the incredible heat of their dragonflame.

This is because dragons throw off so much heat that they are warm to the touch, and at night it is said that their bodies steam in the cold. Almost nothing is known about the internal workings of a dragon, including how they generate their flame, but whatever is happening inside a dragon makes their exterior as warm as an oven. This is why they are ready to strike on a "Dracarys" moment.

A dragon's power comes from their flame, and it seem that fire is always raging inside of them, ready for use. (This would also explain why their own bones are immune to fire.)

There are many theories about where dragons come from

No one knows exactly where the first dragons came from, or even how they came into existence. Dragons are native to Essos, and there are legends from far north and south about them having once lived there. Ancient dragonbones have even been found in some of these places.

There are those who say that dragons came from the Shadow Lands beyond the mysterious city of Asshai, home of many red priests and priestesses. One theory says that  they were brought there by people so ancient that they don’t have a name.

In Qarth, the legend is that dragons came from a second moon that was opened by the heat of the sun, resulting in a million dragons being released. There was an archmaester who believed that practitioners of blood magic made dragons from wyverns, which are similar creatures that don’t breathe fire.

To this day there are reports of dragon sightings from far away places, though these are never confirmed. The truth of how dragons came into the world thousands of years ago will likely never be known-- it is just another of their many great mysterious.

The Valyrians claimed dragons sprang forth from the Fourteen Flames

The greatest dragonlords that the world has ever known were the Valyrians, and they had their own tale of where dragons came from.

The Valyrians were once sheepherders... until the day they found dragons living in the chain of volcanoes on the Valyrian peninsula known as the Fourteen Flames. Like all the legends of how dragons came into the world, no one knows if this is true or not. However, is is said the Valyrians thought dragons were the children of the volcanoes, born from the flames of the earth.

Even if this were true, the dragons of Valyria were not spared by the volcanoes when they erupted and destroyed the most powerful city in the world. The Doom of Valyria killed every dragonlord and dragon in the world, except for the Targaryens at Dragonstone and the five dragons they took with them 12 years earlier.

Dragons might only allow people of Valyrian heritage to ride them

Not just anyone can ride a dragon, and many have died in a bath of dragonflame trying to mount one. Some maesters believe that dragons are as intelligent as men, but that they have a different kind of intelligence that we can’t fully understand. This is why no one knows exactly why a dragon will allow one person to mount them but not another.

However, some believe that being of Valyrian descent is a factor in this connection, and explains why relatives and bastards of House Targaryen are able to become dragonriders.

There may be an innate relationship between dragons and those of Valyrians ancestry. However, it is unknown whether this is because they were the first people to find the dragons or because they made dragons using their own magic.

Drogon got up close and personal with Jon Snow, who is secretly the son of Rhaegar Targaryen. Drogon seemed to innately understand that Jon himself has the blood of the dragon, even when the rest of mankind has no idea.

We might never really know why dragons let some people ride them, but for now we can only assume that it is because their riders also trace back to Valyria.

Dragons might be able to sense when their riders are in distress

Dragons and their riders have a special relationship, but it might go well beyond a physical connection.

The dragonrider Queen Helaena Targaryen died by suicide when she jumped from her window in Maegor’s Holdfast in the Red Keep (unless she was murdered), impaling herself on the spikes below.

At the same moment across the city in King’s Landing her dragon Dreamfyre is said to have risen with a roar so loud it shook the entire Dragonpit where she was locked up. She was so distraught that she managed to break two of her chains. Dreamfyre seemed to sense the death of her dragonrider at the moment of Helaena’s demise, despite not being anywhere near her.

This connection might also work in reverse. In the novels, when Drogon was struck by a spear by the Sons of the Harpy during their surprise attack in the fighting pit of Meereen, Daenerys screamed out at the same time he was hit, as though she herself had been struck.

The bond between a dragon and its mount seems to be far more intense and intimate than that between any other person and animal. Both dragons and their riders seem to share in each others' pain.

They might not have a fixed gender

The anatomy of a dragon is one of the many great mysteries about them, including how they reproduce. (It’s hard to dissect an animal that is basically living fire). We know dragons lay scaled eggs, but all of their reproductive organs are internal, so no one knows how the process works.

Some maesters, like Maester Aemon Targaryen, believe that dragons are gender fluid, able to transform back and forth between male and female when needed (sort of like those frogs Dr. Grant talked about in Jurassic Park). Any dragon seen laying eggs is referred to as a she-dragon, but this might not be accurate if they can easily switch genders.

No one even knows the real mating habits of dragons, which only adds to the confusion and conflicting theories. It’s hard not to think about the non-gender specific prophecy about the Prince That Was Promised (High Valyrian does not have gender specific pronouns) when thinking about how dragons don't seem to be male or female.

Could the prophesied Prince end up being a dragon, since dragons have no fixed gender?

Valyrians learned the secret art of controlling dragons and used them as weapons

No one knows whether or not dragons existed before the Valyrians, but nobody used them to create an empire the way that the Valyrians did.

The Valyrians somehow learned how to control dragons, who are notoriously temperamental and stubborn creatures. Dragons tend to obey more when they have been fed, but that doesn’t explain how the Valyrians were able to master them.

Some think that the Valyrians used magical spells, while others believe that they used magical horns. This is what Euron Greyjoy claims to have found in the novels-- a huge, ancient horn known as Dragonbinder.

Whatever their methods were, they used dragons to defeat the old empires of Essos, such as the Ghis and Rhoynar. They built the Valyrian Freehold, the greatest empire the world has ever known, and they did all of that because they didn't just own dragons, but they also knew how to control them.

Dragons fought each other during the Targaryen civil war

The first Targaryen civil war is known as The Dance of the Dragons because it featured dragons doing battle with one another over the skies of Westeros. The legends of those dragon fights are some of the most amazing in the entire history of the Seven Kingdoms. However, the war led to the death of many of them, and helped lead to their extinction from the world.

Half-brother and sister Aegon II and Rhaenrya fought over the Iron Throne following the death of their father King Viserys I. There were 20 dragons when Viserys died, the most ever in Westeros at one time. By the end of the Dance only four remained, and within twenty years the last dragon, which only reached the size of a cat, died too.

Size advantage was the primary factor in many dragon fights, though speed helped too. Dragons had success attacking one another by going after their throats, since their massive jaws and huge teeth were one of the few things that could penetrate their thick scales and strong bones.

Dragons and their riders have exclusive relationships so long as the rider lives

Part of what makes the relationship between dragons and their riders special is that they are always exclusive. A dragonrider will never attempt to sit on the back of another dragon, and this was even true of Aegon the Conqueror, who never sat on one of his sister-wives’ dragons. It works the other way as well, because a dragon will never accept another mount while their own rider lives.

The connection ends when a dragonrider dies, though. Aegon was not the first Targaryen to ride on the back of Balerion the Black Dread, nor was he the last. The incredible lifespan of dragons would make them mostly useless if they didn’t accept anyone else when their rider died.

The unknown reasons why a dragon allows a certain individual to ride them and not others only gets stronger once this connection is made. It is also why, in the novels, Daenerys is obsessed with the idea of three heads of the dragon. She needs two other people to ride Viserion and Rhaegal because she can't (though now she might be able to at least ride one of them).

They can be killed

Despite their size and power, dragons have fallen in battle before. During the many wars waged by Valyria in Essos, dragons were sometimes killed.

Throughout the Second Spice War between Valyria and the Rhonyar, Prince Garin and his forces managed to kill three dragons during a battle. It is said he used water wizards to bring them down.

The Valyrians returned, though, this time with 300 dragons, and won a final and decisive victory over Garin. This is  not the only recorded death of a dragon in war, however. Long before the Dance of the Dragons, Westeros also saw a dragon fall in battle.

Aegon never truly conquered the Seven Kingdoms, because Dorne managed to withstand his assault mainly by hiding and refusing to meet him on the battlefield. When his sister Rhaenys attacked them, however, they managed to bring down her dragon Meraxes by firing a scorpion bolt through its eye.

The dragon crashed to his death, killing Rhaenys too. This was the same type of weapon Bronn used to shoot Drogon at the Loot Train attack, only his aim wasn't quite as deadly.

Additionally, when the Night King fired his ice spear at Viserion, the dragon was immediately mortally wounded and sailed down to his death.

There are legends of ice dragons

The lives of dragons are shrouded in legend and mystery, but no one ever doubted they existed, even before Daenerys brought them back to the world. However, there is another type of dragon that many believe are just legend: ice dragons.

Old Nan used to tell the Stark children about ice dragons, which were said to be even bigger than the dragons of Valyria. The legends say they were made out of ice itself, and they had blue eyes and clear wings. Jon Snow often thinks of them in the novels while he's at the Wall, noting how the howling winds there are like the icy breath of an ice dragon.

Some legends even say that there is an ice dragon trapped in the Wall itself, and it will be freed if it ever comes down.

No one knows whether or not ice dragons ever existed. However, the Giants and the Children of the Forest were thought to be myths too, and now they've returned to Westeros to all to see.

However, with the death and reanimation of Viserion by the Night King, it is clear that ice dragons are not merely legends of the past. Though no character has witnessed the ice dragon yet, it is sure to bring big problems for Westeros in the future.

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Do you know any other interesting facts about Game of Thrones's dragons? What do you think of the first ice dragon? Let us know in the comments!