Walk forward until you come to a slightly open space with a Club in front of you (there's a Red Orb Chest in the building to the left). Go to the right and you'll find two White Chests with a Gorgon Eye and Phoenix Feather in them. There are also two doors you can break open to reveal two Red Orb Chests. For now, bypass the Club and you'll be blocked by barriers and have to fight a new enemy, the Juggernaut.
The Juggernaut isn't too hard, when it's one-on-one, but you know that's not going to happen. Soon after it appears, two mini-Cerberus show up, which aren't too much trouble. The Juggernaut can grab you, which will require you to attack until you break free. It can also pound the ground, sending out a short shockwave that can damage you. One last attack is when it charges and tries to hit you, but that's easily avoided by constantly moving.
Not long after the first Juggernaut appears, a second will show up and join in the fun. This is where things can get a little bit hairy, but don't get too greedy and do short attacks until you see the red bar appear. Grapple it to start a mini-game where you have to attack it and then dodge when it tries to attack you. It should only take a few more attacks after to kill it, where it will yield Green Orbs in addition to red ones. Note that successfully doing this mini-game will earn you the Open Minded trophy.
With all the enemies dead, go to the end of the path on the right to find a movable block. Don't move it just yet, but jump on top and then on the nearby ledge to find a breakable door with Circe's Vial and a Phoenix Feather behind it. Pull the block all the way to the left to see a Red Orb Chest on top of another building. Ignore the block and go to the end of the path to find a Green Chest and a crank. There's a Gorgon Eye behind the gears, so grab it and then turn the crank to lower a rope.
Go back to the ledge with the Red Orb Chest and get back on it, then use the rope to get across. Jump up and grab the Javelin if you want, then cross the bridge. As you cross it, Megaera's bugs will spawn on the opposite end. Kill them, then use the ladder and the beams to climb across to the next area. There's a wooden ledge on the right where you can break a door to find a Red Orb Chest.
In the open area at the end, with the giant flaming door, press R1 at the fire to obtain the Fire of Ares. This will give your Blades of Chaos fire elemental attacks, as well as give you access to your first magic. Kill the Satyrs that appear with your newly found powers and once they're all dead, the door will open.
Go down this long hallway, grabbing the Green Chest if needed, until you come to a big clearing. You'll have to face off against a Satyr General, with some spear tossers on a ledge in the background, which should be your first priority. After that, some sword-wielding ones will spawn and you won't be able to grapple them, as they have armor on. An easy way to dispatch the General is to stand on that ledge and use the Triangle move that launches enemies in the air, then get a couple hits in. When you see the red bar appear, jump down and grapple it to start a QTE that will kill it.
Once all the enemies are dead, jump up to the two ledges on both sides to find a total of 3 Red Orb Chests, as well as a White Chest with a Gorgon Eye. Jump up and then across the broken bridge, where you'll find a Sling on the ground. Use this if you want to kill the Harpies and other enemies, then continue. Open the alternating chest for either magic or health, then jump up and grab the rock to start climbing.
When you reach the top, take out the enemies and go behind the giant wheel to find two Red Orb Chests. Go back around to the front and grapple the item in front of the wheel and start walking backwards. Once you reach the end, let go and hurry to the wooden ledge on the right, where you can jump onto the cart.
At the top, jump onto the platform and then across to the next area. The path to the left is blocked, so shimmy on the ledge to the right until you get to the next area, where you'll have to fight a few bugs. There's a partially destroyed house on the right with a Red Orb Chest inside, so grab it and then go to the left. As you cross the bridge, it will collapse and you'll have to fight some Harpies and hounds.
After the battle, go to the right and into the building to find a Red Orb Chest and another Gorgon Eye. There's a Green Chest to the right of the building should you need it. Keep going to the right to find a Decayed Chest, but there's nothing you can do about it for now, so cross the bridge and into the building.
Here, you'll find a round room with a giant wheel circling it. Once it passes, follow it and destroy the wood that allows you access to the center. Jump onto this platform and wait for the wheel to pass the left side of the screen. As soon as it does, grapple and pull the chain on the left, then the center and finally the right. Jump back to the circular path and climb the ledges until you get to the platform with two Red Orb Chests and two White Chests, containing a Gorgon Eye and Phoenix Feather.
Pull the chain up here to earn the Round and Round trophy and completely stop the rotating wheel. Drop back down and go back to where the bridge collapsed before to find a glowing spot. Stand on it and grapple the pillar, pulling it down and allowing you to climb up to the next area. You'll now have to fight a Gorgon here.
The Gorgon, as you might have guessed, can petrify you, but it's easily avoided as long as you keep rolling. It can also grab you, so alternate between L1 and R1 to break free. Besides that, it can do a sweeping attack with its tail, as well as smash the ground in front of it with it. Keep attacking it until a grapple opportunity shows, then attack it while dodging until you kill it.
Go through the door and follow the passage until you get attacked by some bugs that come from your left. You can go there to find a mysterious painting, as well as a Decayed Chest, but just continue until you get to The Cistern.