Dragon Prince: Legend of the Guardians of Xadia (Re-Write)

Prologue

Long ago, Xadia was one land, rich in magic and wonder. In the old days, there was only the deep magic, which came from the six primal sources:
The Sun.
The Moon.
The Stars.
The Sky.
The Ocean.
The Earth.
Every living creature in Xadia was born with the gift of magic, a spark inside connected to one of the six primal sources. From the greatest dragon to the smallest insect, magic flowed in their veins.
But humans were different. Humans were flawed. They were born without this gift. Back in ancient times, the humans struggled to survive in the world, while the Xadian creatures thrived. Many humans perished from starvation; others died fighting one another over the scarce resources.
Unicorns were always the most selfless of the Xadian beings. There came a time when, filled with pity, they desperately wanted to help the struggling humans. After all, it was not the humans' choice to be born without magic.
But the First Elves were wary. They warned the unicorns that kindness was not always returned with kindness; it would be a mistake to trust the species. After all, if humans were supposed to use magic, they would have been born with it.
However, the unicorns' compassion ran deep, and they could not be convinced. Despite the elves' warning, the unicorns bestowed the ways of magic onto the humans. They gifted a few wise humans with powerful orbs called primal stones, which contained vast magical energy. Then, they taught them to draw runes to attract and focus the stones' power, and to speak the ancient words used by dragons to release that energy as magical spells.
Finally, humans had the ability to take care of themselves and end their suffering. They fed their hungry, cared for their poor, and healed their seek. As they thrived, they elevated humankind in other ways, learning about the world, the stars, and the arts. They created songs, poetry, and other beautiful things.
But legend tells of a band of noble draconic and elven warriors, known as the Guardians of Xadia. A noble order whose members represented the six primal sources of magic: the Sun, the Moon, the Stars, the Earth, the Sky, and the Ocean, and led by a King or Queen of the Dragons. Whenever trouble is in hand, seek them out, for they are sworn to protect Xadia and all who live in it.
Under their protection, the residents of Xadia lives together in harmony. Safe and guarded from both Xadian-born threats and humans who were banished to the west as punishment for the development of Dark Magic by a human mage, for it uses the essence within magical creatures themselves to unleash dark power, and thus the continent is divided into two. In the east, the magical lands of Xadia, and in the west, the human kingdoms.
For centuries, the King of the Dragons and current King of the Guardians himself, Avizandum, defended the border. The humans called him "Thunder" for when he spoke, his voice shook the Earth and the Sky.
Unfortunately, everything changed when two humans from the kingdom of Katolis, King Harrow and his High Mage, Lord Viren, crossed into Xadia and used unspeakable Dark Magic to slay Avizandum. Then, without mercy, they destroyed his only egg, his heir, the Dragon Prince.
Now, the world stands on the edge of all-out war.