Primordials

"If these creatures were really large enough to break continents apart, it makes me incredibly glad that they are now small enough to be ridden." - Emperor Lunin
After the devastating aftermath of The Cataclysm rippling through the cosmos, the Mortal Realm was had to begin to recover during the Second Age. Then came the Primordial Drakes; great Dragons of immeasurable size and power. Their torsos were the size of mountains; their wingspan the length of a forest. Some scholars contend that these great beasts were the progenitors of all Dragon-kind; others believe they were creatures born from the chaotic energies of the Cataclysm raging across the realms. Regardless of their origins, the Primordial Drakes made their presence known across all of Arkos. Supposedly, there existed one Primordial for each of the elemental magics; their broods would go on to make up the chromatic dragons that now plague the various biomes of Arkos.
It is said that the Primordials were extremely territorial, often battling with the other Drakes and their broods on whatever they set their eyes on. Due to their enormous size and power, many believe that the Primordials are responsible for breaking apart and shaping the continents of Arkos in the way they are presently. Many mortals unfortunate enough to be in the general vicinity of a Primordial was either obliterated, or appealed to the drakes' massive egos by worshipping it and pledging their feable services to it.
Surviving Second Age records tell of a group of powerful mages known as the Cosmic Council that eventually were able to kill the Primordials before they ravaged the planet, though the group suffered many losses and presumebly has long disbanded.