Douluo Dalu 2: The True God King - Chapter 231: [DD2]:

Summoned after an unfortunate accident in hopes they could protect the world from a coming threat, Ben and his classmates are gifted another chance at life. With fame and fortune promised to whoever is willing to fight for the sake of the world it doesn't seem like a bad deal, there's just one small problem. Ben wasn't blessed with any magic or combat skills, just crafting and enchanting. While the skills themselves aren't useless they also aren't seen as being necessary to the coming war. Now not needed and alone Ben tries to find a place in the world while meeting some of its colourful characters along the way.

The most precious things in the world are priceless. Ordinary men tend to turn a blind eye to this fact. Apart from the treasured air, sunlight, and familial love, there is still one more thing that’s extremely valuable. It’s right beside you and can be easily obtained.

- Description from Novelupdates

This is a world where a king is the most powerful.

Kai of the Sorcerer’s Tower is one of the last mages left, barely surviving in a world ruled by creatures of the dark — where the era of mages ended, and most of the lands got contaminated with dead mana. To save his world and fulfil his master’s last wish, he put himself through a forbidden ritual, risking his soul being ripped into pieces to make his way into the past. In an era with abundant mana — an era yet to enter the Golden Era of Magic. Things go wrong, of course, as they always do, and he finds himself thousands of years before the world fell to mana contamination — in the body of a young lord, Arzan. All is not well, though, as the young lord was murdered by someone right at the cusp of a beast wave threatening the territory, while larger threats loom on the horizon. There was a lot to do for Kai to regain his former strength in this time of primitive technology, but then again, he might just be able to change that.