I Studied Abroad in the Modern Times - Chapter 171Book 2: : Retired but Rehired

There was once an immortal cultivator fighting for the fate of human beings. Unfortunately, he failed that time; but fortunately got another chance as he was reborn once more as a human, on the earth of 5,000 years ago. With a second chance, he not only would embark on the road of saving all mankind, but also would retrieve his human nature on the new journey that would last for 5,000 years.

- Description from Novelupdates

The main character has been reincarnated, and he possesses a system and a powerful treasure. Using these, he plans to create his own universe. Keep reading to find out more.

After announcing it will be discontinuing all service, the internet game ‘Yggdrasil’ shut down… That was the plan, but for some reason, the player character did not log out some time after the server was closed. NPCs start to become sentient. A normal youth who loves gaming in the real world seemed to have been transported into an alternate world along with his guild, becoming the strongest mage with the appearance of a skeleton, Momonga. He leads his guild ‘Ainz Ooal Gown’ towards an unprecedented legendary fantasy adventure!

Ethan wakes up expecting to see the walls of a hospital room—only to find a system message blinking in front of him:[Ding! You have killed a green worm][Ding! Green worm has been added to your summoning list]