The story centers on the titular Clevatess, the lord of Dark Beasts, who wields both uncanny intellect and destructive power. Frustrated by the 13 heroes tasked to destroy him, he has decided to be rid of humanity once and for all. However, he has been charged with one nuisance: he revived a hero he personally slayed and adopts an orphaned humanoid baby—the last hope to save a dying world. The world stands upon the brink of Armageddon, with the obligation of raising one child holding it all back. Now bound together, what fate awaits this unlikely trio? 
 
(Source: Anime News Network, Crunchyroll, edited)
 
Note: The first episode aired with a runtime of ~46 minutes as opposed to the standard 24 minute long episode.