A brief description of the manga The Reincarnated Sage who was abandoned ~I will create the strongest Demon Empire in the Demon Forest~:
When dying, the great sage used the new magic that he developed to be reborn in the future. However, after the rebirth he was considered mediocre and left in a forest full of monsters, but the goblins decided to take him and grow him. And to give them his duty, he helped them develop and taught them magic. The story of an abandoned child who will build a great empire of demons!