Became the Unjust Contract Slave of the Archamage's Book - Chapter 18

Mo Zhu’s mother remarried after her father went missing, and she had lived in the countryside with her elderly grandmother ever since. The girl who had no parents wanted to protect herself. Therefore, to avoid getting bullied, she had turned wild since she was a child—she played truant, fought, and drank. There was nothing she did not know how to do. She was a problematic student in the eyes of her teachers, a big sister in the eyes of her classmates, and a hooligan in the eyes of her acquaintances.

Ye Xiwen was previously only an ordinary university student on Earth, but unexpectedly crossed through into the world known as the Zhen Wu Jie world! In this world, formidable warriors are capable of turning over mountains and collapsing the ocean, destroying the sky and extinguishing the earth! He originally had ordinary aptitude, because of that he received the mysterious special space! Any martial art can be deduced within the mysterious space, other people practice for decades, he only needs a year! So long as he has enough spirit stones, any talents he faces are all floating clouds!

- Description from Novelupdates

After forming a blood pact with the Saint and Demon ladies, the good-for-nothing young boy obtained the Yin-Yang divine veins, learned the art of alchemy and martial arts, and dominated the world.The young Shen Xiang had a romantic encounter with a goddess and a witch, and obtained their supreme inheritance, acquired a divine vein that defied the heavens, learned peerless magical skills, and mastered superb alchemy techniques, which made him very successful on the road of martial arts... When he was hungry, he would refine some pills as snacks, when he was lonely, he would flirt with the high and mighty goddess, when he was bored, he would play with those martial arts masters who came to ask for pills, and when he was tired, he would let the delicate wives around him give him massages...

What would you say is the most valuable thing in this world?