While Others Cultivate, I Use My Multiverse System - Chapter 11: Invasion

The protagonist, a renowned gamer/YouTuber aka [TorchDancer] is a master of the game “Tril Trilo Trilogy.” When offered a chance to playtest the prequel, “Part 0,” he jumps at the opportunity. But a twist of fate plunges him into the game itself, transforming him into the series’ ultimate villain, Frank Wonderstein. Trapped in a monstrous body, he must navigate a dangerous world, unraveling the secrets of the game and his own destiny. Can a hero become a villain? Or can a villain find redemption? Well, you’ll just have to read to find out.

A series of short stories in the world of Toaru Majutsu no Index organized into chapters featuring Kanzaki Kaori as the protagonist, going around the world and space doing missions for the Church of Necessary Evil, however, there is more than meets the eye as each incident is connected.

One chapter was bundled with each limited edition release of the Toaru Kagaku no Railgun anime DVD and BDs, with all of them together being equivalent to a single normal Toaru Majutsu no Index volume

What happens when a fanfic author with a habit of lying and scheming suddenly finds himself as a self insert during Duelist Kingdom? What happens when you have Yugi, Joey, Kaiba, and the rest encounter someone who knows all about every major player in their saga... and sees no problem with abusing said knowledge? Chaos, dear reader. Sweet, sweet chaos

He was once Head of the Immortal Sects.

Jiang Zheliu resisted the world’s destruction, protecting the people single-handedly. After losing all his spiritual energy, his hair turned white overnight.

All that remained was a millennium passed in vain, and a grave disease.

He distanced himself from the Cultivation World, went to Zhongnan Mountain to collect herbal medicines and grow flowers, as if to retire.

Until….. Those little demons he had once saved, his cherished juniors, even those devils that he had suppressed innumerable times, all came knocking at his door, each more excited than the next gripping his hand:

“Qianbei, what type do you like? Can you not be so rigid on your requirements?”

Jiang Zheliu: “……？？？”

Wenren Ye is newly appointed Devil Lord of the Devil Realm.

He is cold-hearted, devilishly handsome, and when he was younger he suffered a humiliating defeat at the hands of a certain Head of the Immortal Sects.

Still obsessed with this defeat, Wenren Ye hurried through the night to Zhongnan Mountain, but all he saw was white-haired weak Immortal Sects Leader, with droopy eyes, sick to the bone, with freshly coughed up blood staining his lips.

His obsession was still alive, but his heart was also thumping.

- Description from Novelupdates