Not too long ago, the people responsible for making the Mechdragons and other powerful machines created what they thought was their magnum opus, a dragon made of a Magic Stone alloy named Ninegaruda, so named because he was nine times as powerful as any of the other Number Dragons. But this did not last, as Ninegaruda, after being enraged, went on a rampage that simply would not be quelled, causing mass destruction across the catacombs that many people call home. The dragon's immense power was turned on its creators, as even with assistance from Miru, one of the most powerful of Dragonbounds, the beast's Magic Stone hide could not be pierced.
The most prodigious of these people banded together to try to end the destruction. But how? Even if a local Dragon Tamer tried to calm the beast, only a Dragon Caller or a Dragonbound can truly control monsters, as Dragon Tamers merely cooperate with them, and the poor fool would be ripped to shreds. A Dragonbound must make a pact with its dragon before it gains its power, and Ninegaruda was certainly in no mood to do that. And Dragon Callers train for years in Starlight Sanctuary before they master the art of Dragon Calling, and the dragon chooses the caller. In addition to this, a human body can't host a machine, and thus can't make a Dragonbound pact with it. But...that was the answer to the problem! Why get a Dragon Caller when you can make your own?
Using data contributed from Dragon Callers and Dragonbounds from all over, the geniuses worked and worked for months and months, but all the while Ninegaruda's anger grew ever greater. And after an innumerable amount of work, they had done it. The first ever artificial Dragon Caller, made to fit Ninegaruda in every way. She rivaled the power of even the Steel Star Deities, as with just a little bit of power, she could burn down the equivalent of 21 football fields! Her name? Ena.
They took Ena to Ninegaruda's last known location, then fled. An hour later, Ena came out not only with the dragon quelled, but riding and cuddling it! The two were inseparable after that. The scientists didn't know what to do with her and shutting her down just seemed wrong and cruel, so they let her help out to possibly avoid any more machines going rogue. However, Ena insisted that Ninegaruda helped her as well. The scientists, though skeptical at first, obliged, as what was the harm? And Ena was happy.
Then one day, Ninegaruda was taken away for a period to study him, in an attempt to see what went wrong. Not long after, Ena started acting strangely, lashing out at her fellow "employees," things like that. A scientist came in to see what was wrong with HER, and found a lot of spiteful thoughts in her data. She thought nothing of it. The next day, the scientist was found in critical condition of the floor, and Ena and Ninegaruda had vanished. A note was scrawled out found next to spare buster cannon and a purple glove: "YOU TRIED TO DESTROY NINEGARUDA. ANYONE WHO INTERFERES WITH MY DRAGON WILL BE DELETED." Ena had simply been paranoid. And why wouldn't she? For if a Dragon Caller or Dragonbound is removed from their dragon, they're merely a normal human again, even though Ena had much more power than normal humans, even without Ninegaruda.
The mech dragon and robot girl flew for what seemed like countless days, trying to find somewhere suitable for the duo. They endured many harsh conditions, but they were still happy. Until one day, when flying over the southern half of the Split Seas, Ninegaruda had taken enough punishment, and his battery died, sending both dragon and caller tumbling into the dry strait created by Noah himself. With no reasonable way to get Ninegaruda up and running once more, Ena had to carry the body of what was once her dragon, her best friend through the strait with no end and no way to revive him in sight.
Machine Noah was found at the end of the strait. Ena saw her and thought she was her ticket out by sharing some of her power with Ninegaruda, but she refused. Ena, enraged at Machine Noah's selfishness, shot her with enough force that most other Machines would be irreparably blown to bits. This did nearly nothing to her, as Machine Noah, being a very ancient automaton, had seen much more combat than Ena, becoming a master at it, and knew how to minimize damage from other Machines.
Then Machine Noah said, "Be at peace, young one, for you are weakened from your travels.
"I...I am not weak...I am not young. I...I...I made it all the way out here, correct?"
"While the last part's true, i have seen much more than you, and you still have much to learn."
"You...I cannot defeat you because Ninegaruda is inactive. That is all. If...If i had Ninegaruda, you would be dead. Just like those people who would have attempted to take him from me."
"Well, how do you know either of those things? You clearly have more power than you realize, even without the dragon you wield, young Machine."
Ena then had an epiphany.
"You are right."
"Excellent. I'll lend you some of my power so you can get back home."
Ninegaruda was reactivated and flew off with Ena into the now-setting sun. She apologized to her creators, and they too realized that Ena had much more fighting prowess than they had first realized. So Ena now guards the lab from would-be intruders. While she can't do it with Ninegaruda, what does that matter?
It's still their home.