This announcement comes after the season 1 finale just aired. Check out the ANN article for additional information. Synopsis for the first season from AniList:
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?
Unboxious@ani.social 18 hours ago
Overall I liked the first season. I thought the final episode was kind of weak, but I think that had more to do with the adaptation than with the writing. Hopefully the second season will be at least as good.