Awakening of the Old Gods

[Western fantasy + high magic + no heroine + fast pace] Thousands of years later, this continent filled with dragons and magic will still echo the epic of that year. Why does the god help all sentient beings to put an end to his own kind? And why did he leave in such a hurry after being with all sentient beings for a hundred years? The answer to all of this must be found in this land full of stories...