The Indomitable Martial King is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

A world where humans sell and buy otherworldly species as slaves. The great mage Rifenhardt is treated like the Demon King for helping the otherworldly species. A party of heroes arrive to bring down the Demon King! Rifenhardt succeeds in greatly injuring the heroes, but he faces death at the hands of the MARTIAL KING??? Tesslon… “Time and Space Regression Spell.” However, he miraculously manages to cast this last-resort spell and regresses to the past. But… “I became the MARTIAL KING??? Tesslon, one of the heroes who tried to kill me and the strongest on the continent?!” Now begins Rifenhardt’s adventures as both a great mage and the physically strongest man to change the world!