I, The Dragon Overlord - Chapter 522 - Incarnation of Order

On the wedding night, she was tied to his bed.

He Lang died by his own hands for the sake of his imperial younger brother’s ambition, whom he loved. He was offered to be reborn in exchange for giving up his past romantic feelings. Reborn without the burden of his romantic feelings, he brings with him a manual to new worlds. He wholeheartedly followed the instructions of the manual to complete the tasks, not knowing that the originally slag gong was blackening…
He pleaded to his affectionate Emperor brother to release him, he pleaded to the paranoid prisoner next door, but until the end he remained baffled.
In the end, he discovered that the full name of the manual was – “Slag Shou Cultivating Manual”
Σ (っ ° ° °;) っ!

- Description from Novelupdates

Roy died during a war against the Evil God Cult, but somehow, he returned back in time to 30 years in the past where he was just a boy who awaken his summoning magic.

Enemy of the world, cursed by all, Kim Sungchul goes on a quest to prevent the ‘prophecy of the end’ from coming to pass.

But no matter how much he raised his strength, there were still some things he could not achieve with physical strength alone.

Resolving to obtain the power of magic, he goes into hiding to learn magic from his most hated of enemies, The Mages.