This chapter begins with you thrown into a battle with a Cerberus and a bunch of enemies with weapons. Try and take care of the Cerberus first, as it's large and can be a hindrance when moving around. Once everything is dead, go to the gate and use the Amulet to heal it.
Go forward a bit and go up the stairs on your right to find a Red Orb Chest and a Gorgon Eye, then go to the left at the end of the first hallway to find another Red Orb Chest and a Phoenix Feather. Go into the cage and press R1 to go through the door for a cutscene.
After the cutscene is over, turn around and go near the door you entered to find the Orkos' Cloak Artifact to the right of it on the ground, then heal up and go through the gate. You'll be fighting an Empusa, which is a new enemy that has a tendency to leave a poison circle on the ground, so stay out of it. Once it's dead, climb to the top, where you'll face some more enemies.
Kill them, then drop down and kill some more enemies. With them out of the way, go to the end of the walkway and use the Amulet to heal the structures. You'll now need to jump down and when it slows down, grapple the green spot and keep double jumping to each grapple point until you get to the top. Go down the stairs, through the gate, repairing the Decayed Chest (Chest #6) and then down the ladder to enter the Martyr's Chambers.
