Greek Mythology: I open a treasure chest at Olympus - Chapter 3: Intermediate treasure chest, treasure chest system

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

A story following a young hunter named Jay. He has grown up in a world where dungeons, monsters, and humans with leveling systems are a cultural norm. At the age of 20, he awakens a skill that allows him to steal the abilities of monsters. While others are stuck with a specific skill set, he continues to grow stronger after every battle.

Follow Jay's journey as he learns more about his unique situation in a world that's grown blind to the real dangers of modern-day dungeon diving.

A useless prince, yet brimming with kindness and compassion—his smile as warm as sunlight, illuminating this darkened era.But that was merely a mask, hiding the poisonous and mad nature beneath.A monster lurking behind a gentle shell.A system that feeds on stolen Heroines.He will outplay destiny—and rise as the world’s ultimate villain.