As a demon king, create a secret game in another world

Lin Fei came to a different world by accident. People here can awaken their professions [Warrior] [Assassin] [Monk] when they reach the age of 15.
As a time traveler, Lin Fei awakened a unique profession [Demon King] and gained the ability to create secret realms.
Let me bring more fun to this world.
So, Secret Realm: Winter is Coming: The Blade Stands Above the Realm.
Secret Realm Fulong Tree: The Rock Dragon King is shaking the earth
Secret Realm: The Gospel of the False God envelopes the world.
Come, for power, wealth... everything is in the secret realm.