Reincarnation of the Hero Party's Grand Mage

The warrior Lista heard the rumors about the great magician Rin, hailed as a genius for becoming the youngest 4-star mage. Lista recruited him to join her party to fight the forces of the void but, right before the final battle, Rin’s body succumbed to the void’s dark poison. As he drew his last breath, Rin cast an immortality spell, encasing his body in ice and promising Lista that he would return. Rin kept his promise and returned after 300 years--but reborn in the body of a noble boy.

Source: Tapas Includes 31 extra chapters.