Under the veterans' lead, the group quickly cleared out the entire Abyss Underground Palace. The Abyssal Demon Palace built in this area was also pushed down by the group and turned into ruins.
Then, they used the power of the key again to open the door of another abyss underground palace that had yet to be conquered. They joined the Professional team that was sweeping through the abyss underground palace and helped them defeat the Fallens and Abyssal Demons that resisted in the abyss underground palace.
Just like that, the group of people killed their way to countless abyssal underground palaces, killed countless Abyssal Kings, and killed countless Abyssal Demons and Fallens.
Finally, they had gathered all the palace keys of the Abyss King and obtained the authority to open the Abyss King's bedroom.