The System Asked Me to Take in the Boss

Was he expelled from the school just after traveling through time? Has your cultivation level been abolished? Fortunately I have a system. Ding, congratulations to the host for taking in a Drought Demon from the Zombie Realm! Ding, congratulations to the host for taking in a peerless swordsman from the sword world! Ding, congratulations to the host for taking in...! This is a story about the protagonist Bai Yun leading his adopted people to explore the major worlds and establish a power in the main world to compete for hegemony!