Murim's Weakest Princess - Chapter 18: Nature of Qi

Forge unparalleled mechs with the ambition of old age, and use the galaxy as a knife to smash the edge of the empire.

His name is Ji Xinghe. When he was 65 years old, he went to Alien Battlefield to avenge his son.

The old man is standing on the ground, his ambition is a thousand miles away, the old man wears armor, and fights to the galaxy, the old man drags his sword, it is not for glory.

- Description from novelbuddy

The world was once at war with 10 alternate worlds. This was known as the Concept War and our world won 60 years ago. All of this was concealed so no normal people are aware of this fact in the current time.

After the death of his grandfather, the high-school student Sayama Mikoto is suddenly summoned by the giant corporation IAI. He learns this world is headed for destruction due to the acceleration of the Minus Concepts. To prevent this, negotiations must be undertaken with the survivors of the other parallel worlds so their 10 concepts can be released.

And so Sayama is caught up in the final battle to clean up after the Concept War which left behind so much enmity.

An ordinary office clerk was accidentally reborn into a vast and mysterious world of Xianxia, becoming a member of a small cultivation clan.The story begins in an endless sea of sand, in an oasis called the Yuquan Lake Oasis.

Taking place within a world of Measurements―superpowers owned from birth, with most being absolute trash.A world involving numerous secret organisations looking to take advantage of those rare and remarkable few possessing exceptional powers.When there exists Forbidden Knowledge better left unknown.When the discovery of said knowledge results in the inevitable; a world-ending catastrophe.‘Ignorance is bliss.’Fighting against the unrelenting persistence of the one who knows all.Before the tragic fate of the world repeats itself once more.―He must be stopped.