Xerox Zee : An Extra into a Novel - Chapter 34: Partner?

As a promise, he went out into the world as an assassin. 3 years later, after becoming the Supreme Assassin, he gave up on everything he had and returned to the ranks of ordinary people. But one day, Kismet, a mystical game created by the National Research and Development had appeared.

Enigmatic hands, spectral frame, and one cunning strike just like the swing of the Grim Reaper. The Supreme Assassin takes on the mystical world, and how his legendary tales sets off, progressively ascending the altar to becoming the best.

- Description from Novelupdates

An ordinary office clerk was accidentally reborn into a vast and mysterious world of Xianxia, becoming a member of a small cultivation clan.The story begins in an endless sea of sand, in an oasis called the Yuquan Lake Oasis.

Lucius was a man born to a pair of lowly servants that worked for the Great Demon worshiping Barrom clan. Growing up in the harsh conditions of the Barrom clan where magic and power reigned supreme, he weathered though humiliation and schemes. Knowing that he wanted to be the oppressor than the oppressed, he began his conquest. Not averse to betraying or scheming, Lucius made use of his allies as mere pawns to be sacrificed.

Learning that a powerful artifact lost eons ago was hidden in an ancient ruin, Lucius betrayed and sacrificed one of his closest people, his lover without hesitation.

But he didn’t know that fate had a different plan for him and the artifact he had yearned for would send his soul hurtling across the cosmos, forcing it into the broken body of a young man called Asher Inanis. Coming to his senses he finds the world to be completely different where the magic of his previous world did not exist, but what did was ‘Gifts’.

Witness how he learns about the world, gains power and reigns supreme against all odds becoming the Demonic Sage.

Reborn in World of Warcraft : Mastering All Beauty