In the "Little Lost Girl" Easter Egg in Call of Duty: Black Ops II, what's the last step required for the achievement?

The last step required for the achievement in "In the Little Lost Girl" Easter egg in Call of Duty: Black Ops II is to activate all three staffs and press the action button on the door inside the Crazy Place. This will open the portal and transport the player to Agartha, where they must survive waves of zombies and then defeat the final boss in order to escape. The phrase "Raise Hell" is often associated with causing chaos or creating a disturbance, and in this context, it implies that the player needs to create mayhem by defeating hordes of zombies and ultimately defeating the boss to complete the Easter egg and unlock the achievement.