Once you've made it past the spike room, you'll come to a room containing flames that constantly sweep through. Before you proceed, be sure your health and magic meters are both completely full by using the two chests at the end of the hallway. Before entering the large room, grab the statue next to the doorway and get behind it. Start pushing the statue into the large room.
There's a Phoenix Feather (or Red Orb chest) in the gated area off on the right side of this room. However, if you have already collected 18 Phoenix Feathers, it would probably be best to just leave this one alone.
Drag the statue over to the right side of the room. Remain behind it to shield yourself from the damaging flames. Move it around the first set of raised tiles. While you move the statue, an Elite Legionnaire and a couple of Harpies will pester you. Petrify the Harpies with the Head of Euryale, which will cause them to fall to the ground and shatter. The Harpies continuously respawn, but kill them to get them off of your back for a short while. A fully upgraded Head of Euyrale would be great for this part, but it's not entirely necessary. You can petrify and shatter the Elite Legionnaires too, but it requires a bit more from your magic meter. Switch to the Barbarian Hammer and use it to shatter a petrified Elite Legionnaire.
Drag the statue around the set of raised tiles in the middle of the room, and place it in front of the tile that has a lever on it. With the statue shielding you, pull the lever to lower the raised tiles up ahead. When you push the statue over the lowered tiles, two Elite Legionnaires will spawn. Use the Head of Euryale to turn these enemies to stone and shatter them with the Barbarian Hammer. If your magic meter happens to be empty, remain behind the statue and fight them off with the Barbarian Hammer.
Once the Elite Legionnaires have been dealt with, push the statue onto the push button on the left. Wait until flames sweep through the room, then move over and stand on the push button on the right. A grapple point lowers from the ceiling right in front of you when both push buttons are pressed down. Press the R1 button to swing onto the ledge ahead to avoid the next row of flames.This video is from our unofficial game guide. You can view the full guide here