What Should I Do If I Become a Demon Lord After Being Undercover for Three Months?

After traveling to the world of Xianxia and becoming a righteous disciple, Lu Xuan was ordered to go undercover in the Demon Sect. He thought he would be in trouble but he didn't expect to activate the sign-in system. There will be rewards for signing in. The more extraordinary the location, the better the rewards. The first time he signed in at the Demon Gate Mountain Gate, he obtained the Supreme Sword Heart, which made him famous, and he has been out of control since then... Sign in at the Sutra Pavilion and gain a hundred years of cultivation. Sign in at the forbidden area of ​​​​the back mountain and receive ten thousand swords to return to the clan. … A month later, he became the most outstanding disciple of the Demon Sect. Two months later, he was accepted as a direct successor by the sect leader and became a strong contender for the next sect leader. Three months later, the sect leader went crazy. He lived up to expectations and became the new sect leader! "I have only been undercover for three months and I have become a demon lord. What should I do now? It's very urgent to wait online!" This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.