After The fall of Lucifer, The four Lords of Hell Land started fighting for the Crown, they believe that finding the lost infernal sword will give them the power of controlling all demons, Blinded by their greed the balance between the two Worlds is disturbed and Black Portals started to appear.
Meanwhile, before his death, Lucifer charged his loyal servant Argos to take care of his son in the secret Castle and to train him to become the next demon’s master.
https://illithas.itch.io/room-101
Source: itch.io