Archmage Transcending Through Regression

Mikhail Walpurgis, the world's only 9th-circle Archmage, fell in battle due to a damned hero, and managed to cast one final advanced magic spell, "Time Reversal." As time rewound, he regressed to 20 years ago.
"Fine. I'll just become the hero instead."
(Source: Kakao Entertainment Corp., translated)