MTL - Arcane Age - Chapter 554 Pool of the Styx

Shen Ningning died of exhaustion after being dared to run a marathon. She transmigrated into a savage, unfamiliar world where humans struggle to survive among beasts. Before she could despair, she discovered she was bound to the Peak Body Survival System.The system believes survival is nothing more than physical training. Hunting, fleeing, gathering food, and even fear are all treated as endurance tasks, with failure punished mercilessly. Trapped in a dangerous world and forced to follow the system’s rules, Shen Ningning can only struggle to survive one day at a time.Her situation worsens when a powerful snake beastman claims her as his mate and refuses to leave her side. As danger closes in from both the wildlands and the system itself, Shen Ningning must find a way to live in a world that demands strength—whether she is ready or not.

Leon was supposed to disappear.On Earth, he was nobody.In this new world of cultivation, reborn into a body that wasn’t even his own, he was less than that — a forgotten teacher exiled to the quiet heights of Amethyst Summit Division.No glory.No backing.No destiny.Until the Grand Return System awakened.Every resource he gives… returns a thousandfold.Every treasure he parts with… comes back stronger.Every disciple he nurtures… becomes a storm the heavens cannot ignore.While the sect mocks him as a useless master wasting potential, Leon calmly shapes a silver-haired girl born with Divine Ice Bones into something terrifying. A legend in the making. A blade pointed at fate itself.They see obscurity.Heaven sees a silent calamity rising.Leon doesn’t seek fame.He doesn’t chase thrones.But when destiny finally turns its gaze toward him…The teacher who hid in the shadows will begin rewriting the rules of the world.-----

An ordinary student, a wretched peeper, a cowardly teenager with a kind heart. In a terrorist attack, he inherited the knowledge of countless elites, embarked on a path of God Jagged Tu…

He is an artist!

He is a mathematician!

He is a psychology Doctor!

He is a master of fighting!

In fact, he is a man

Taken off raw site:

A wretched, dirty young man is working during the summer when he was caught up in a mysterious explosion. After that explosion, the young man is then left with the memories and knowledge of dozens of the world’s experts.

He has changed, his heart has become cold, iron-blooded. He became a killing machine, his mind turned mechanical, calculative. Everything goes according to his plans and calculations!

In this magical, slaughterous world, a door is opened for him…

- Description from Novelupdates

After accidentally falling, she actually finds herself bound to a Second Female Lead Counter Attacking System!