This map can only be unlocked by getting 100% bestiary, which as of v3 does not include the Mobius enemies. This is the only real slaughtermap in the mod, and it throws all the toughest enemies at the player at once. There are watery pits on the west and east sides that are fairly safe to hide in, since only a few of the monsters have line of sight. Let the Heaven Guard do most of the fighting, and use Invisibility and Clock Freeze to fire off a few attacks at surviving groups of enemies and boss creatures.
When everything in the starting area is dead, wall jump up the hollow structures above each watery pit to reach the catwalks above. The catwalks lead to four heavily guarded switches, with boss creatures lying in ambush. Pressing all four switches opens access to the cyan skull, which will open the locked door. After defeating all the enemies in the hallway, backtrack and collect whatever ammo is necessary, because the teleporter is a one way trip.
The percentage counter that appears when the player is teleported to the outer ring applies only to boss creatures. When they are all defeated, the player will be teleported to the exit room. Standard slaughtermap strategies apply here, and long range weapons can be useful. On the opposite side of where the player enters this area is another large cache of weapons.
It is not necessary to get a full kill or item count, as these are not tallied or ranked at the end of the level. It is only necessary to complete the stage to fulfill the requirements to unlock the Infernal Atrocity weapon (This weapon can be found on the NG+ Store back at the base hub). If one still wishes to get a full kill and item count, spare the last surviving boss creature (cast Iron Prison on it) and run around collecting all the potions around the columns, and shooting any weak straggler enemies. Then go back and finish off the final enemy to end the stage.
Average Payout: 27,000 credits