Dragons, Dragonslayers, and Acnologia
The world of Erathalia that Sadalla entered was like nothing he had ever witnessed before. The dragons devoured magicians and beasts with seeming impunity. Contrary to the relatively even playing field that he anticipated where human ingenuity managed to secure their survival, this place was just a giant hunting ground for dragons. Sadalla found a few groups of dragons who were more peaceful and coexisted with magi, but many dragons simply slaughtered them like cattle.
Among the settlements with dragons and humans coexisting, Sadalla was surprised to find stronger and more powerful mages and dragons alike. The most powerful settlements were those of the fire dragons. Despite their fiery tempers and battle spirits befitting their elemental nature, the fire dragons saw consuming humans and lesser beasts as beneath them. Thus, they actively trained with mages and instead ate weaker dragons. The fire mages of this region were beings to be feared, and the weaker dragons eaten by their fiery protectors were no match for the strongest among them. Compared to the Fire Dragon King Igneel, however, they were still mere cannon fodder.
Another settlement, that of Montes Secreta, survived in a very different manner. This was a difficult to find region cloaked in fog. It didn't have many beasts, and generally was not worth much to dragons, so many simply ignored it. Lurking beneath that serenity, however, was a shocking reality. A healer of dragons, powerful enough to mend even the lost limbs of dragons, rested here. Among the humans, he was undoubtedly the strongest by far. Even among the strongest dragons, this mage was a force to be feared. Unfortunately, his dragon protector, Acnologia, was arrogant. He failed to recognize his healer's strength, and treated him as disposable.
Other individual dragons were isolationist. They respected the humans, but also feared the more ruthless dragons, and openly chose to distance themselves from both races. Among them were the Sky Dragon Grendenay, Iron Dragon Metallicana, White Dragon Weislogia, and the Shadow Dragon Skiadrum.
Lastly were the truly benevolent dragons. These dragons truly looked out for humans, and viewed them as equals. Among these dragons, the strongest was Belisarius, the Sage Dragon. Unlike the arrogance of Acnologia, Belisarius believed that the humans were more than mere ants fruitlessly biting at a steel plate, but rather sledgehammers crashing against a mighty wall. They were individually weak, but if enough sledgehammers struck at once, they could rend even the ground itself, destroying the wall with near-impunity. Belisarius sought to harness these humans, and began teaching his magic directly to them, something even the fire dragons refused to even try. These mages trained by Belisarius would become the first Dragonslayers
Sadalla was in awe of both the humans and the dragons. While only a few mages were strong enough and talented enough to learn from Belisarius and the other dragons, those that could became true dragonslayers, unlike the fire mages of Igneel's brood that could only beat weaker dragons.
Sadalla trained his new body for six hundred years. He flew over the continents several times, observing the changes with his ki from altitudes where no dragon could sense him, even if they were sky dragons. Sadalla noticed that the natural energy was increasing, almost as if something was causing it to slowly increase, but Sadalla himself had no idea.
Despite the short period of time, Sadalla had already seen the world undergo an even greater shift than what the firing of the ultimate weapon had wrought upon the world of Pokémon. Just four hundred years into his stay on Erathalia, the dragon Acnologia had gone on a journey away from Montes Secreta, and had betrayed the healer upon his return. Montes Secreta was razed to the ground, and in his rage at witnessing this, the healer had slain Acnologia.
The healer was a popular figure in Montes Secreta. He had a wife, family, and children. He had friends, and a vibrant life full of joy. In a single moment, Acnologia had taken it all away, and then he turned to kill the healer as well.
Consumed by fury at Acnologia's betrayal, the healer became unstoppable. He used his power to slay nearly all of the dragons, culminating in a vast battle at the land of Flowers, which Sadalla had only just witnessed moments ago. Nearly forty dragons had fallen to the mad healer. The man had lost what made him human long ago, and had even forgotten his own name. All that was left in his mind was the name of the dragon who took everything from him, Acnologia. In pursuit of revenge, he had become a true dragon, and he would be forever cursed by the name branded upon him. Acnologia, the Dragon of the End.
Acnologia wasn't feared because he was only going after dragons, of course. If that was all, he would be a hero to many. Acnologia was feared because he also went after the dragonslayers. Acnologia wanted to completely destroy the dragons. In the six hundred years Sadalla had observed them, the dragonslayers had discovered that overusing their powers would directly turn them into dragons. The only way to prevent this was to cling desperately to your humanity with everything you have. Acnologia's hatred had long since made this impossible. In fact, the vast majority of dragonslayers shared this fate. Most were treated as mere weapons by either their villages or the dragons, while others simply had circumstances that forced their hands.
Among the latter category was a truly sorrowful woman. A student of Belisarius, she had married into a tribe nearby, only for them to treat her as nothing more than a weapon. Neither human nor dragon, but a monster. She had become pregnant by her husband, but their mistreatment of her led to her using magic to seal her womb, keeping the baby alive, but preventing it from being born. Upon transforming into a dragon, she managed to stay alive by hiding in the last place Acnologia would ever willingly visit, the ruins of Montes Secreta.