GEARS of DRAGOON 3 ~Ryuukoku no Regalia~

In a world where the land was ravaged by a calamity of the past.
Humanity had built a tower that reached the starry sky and a city in the heavens, and was reveling in an age of prosperity.
But the Empire that rules the tower branded the people left on the surface a "defiled people," and subjected them to discrimination and oppression.

The protagonist, Kyle, born a surface-dweller, encounters the legendary Rebel Dragon, Liberio, in the midst of the resistance movement against the Empire, and comes to inherit its power.
Upon learning that the tower itself is the root cause of the blight, siphoning the mana of the Dragon Veins—the very life of the planet—Kyle takes up the fight to reclaim a land where people can live in freedom.

[From Offical website]