Clear the hall, then turn to the right. When you clear the first batch of mobs 2 serpent statues will rise and spit poison on a cycle. Pass it just like skipping rope. Clear the next room and jump some more poison to the stage portal.
Abyss Sub-Boss: Xixaayx
Room with coffins and poison spitters. Observe the pattern and fight the mobs between them.
If you have the quest Settling a Bet the special statue is in the center of this room. Clicking on it opens a door with a minotaur!
East room has a switch that opens a door and disables the poison-spitting statues. Go back to previous room and turn left. If you run to the statues and jump over them it is easy to avoid the poison.
In the hall with the 4 statues are two holes in the left wall with a Treasure Chest in each.