The Demon Lord's Heir System

Evan Lee travels to a fantasy world and becomes the Demon Lord. Just as the righteous Immortal Sects come to attack, Evan Lee is begged by the members of the Demon Sect to come out and fight them. However, he discovers that he hasn't inherited the original owner's cultivation and is just an ordinary person. Evan Lee can only rely on his acting skills to pretend to be the Lord and bluff his way through. Can't fool them? No problem, I have a system!