You're in a room where you see Phoenix's ashes behind solid bars to the left. For now go through and jump left. Defeat the skeletons and enter the room with spikes coming out of the floor.
Use a lever to lower the spikes. Run quickly towards the opposite wall to the left and hit it a few times to reveal a time-slowing statue. Stop time and go back to a safe position away from the spikes before they reappear. Lower them again and approach a dead soldier's body ahead of you. Take Hail of Boreas and once again go back to the lever. Use it for the third time and use the turnstile (it's where the soldier was), and when you see that the grating to the right is high enough, stop the time and run through it. You might not be able to get through this room in your first try, it takes a little practice.
There are three chests in this corridor - one with a Gorgon Eye and two with red orbs. In order to get to them, jump towards a dark wall a little bit further, grab a ledge, then jump towards the opposite platform.
This is where it gets serious - the most frustrating puzzle in the game is right before you. There're green and blue chests before the entrance - if you don't need them badly, leave them for later. Grab the movable pillar to the left and push it forward. You have to push it towards the lever in the center of the room (and place it a few steps before it so you can safely turn it), and then near the left button at the end of it (then stand on the right one, which will enable you to use the hook to leave the room).
The problem is that you are under heavy fire from imps and irritating, damage-resistant zombies. The single best technique to use here is the Chronos Rage (preferably on lvl3). Use it to stun the opponents and cover yourself when pushing the pillar. If you run out of mana or health, get back to the chests that you left before entering (provided that you did).
At the end of the room there are two buttons: the left one opens the gate and the right one lowers a grappling hook that can get you out of here. To make things easier, place the pillar a few steps before the left button and let the flames push it back so that it activates the button with a few second delay. There are experience chests in surrounding rooms - if you have the patience, do something about them. I definitely didn't.
You finally reached the Phoenix' ashes. Push the run and a platform will be lowered. Push the urn again to place it in an opening, then use the lever at the center of the room. You'll be attacked by some skeletons and overgrown, pig-like beasts. After a cut-scene use one of the air vents to get to the stairs behind the save point on the right. Once you get to the top, look around for a Phoenix Feather and an experience chest. Use the elevator to get back to the courtyard.
Open the door with Boreas' carving. Look in the left part of the next room to find a Gorgon Eye. Climb a rope and blow the horn that you see there. Jump back to the courtyard and use the newly appeared platforms to reach another door.
Use the lever and reach the ceiling. Destroy the two chains that hold the door and pull the movable pillar from the wall. Lower the elevator back, defeat the archers and place the pillar so that it jams the mechanism raising it (it has to be half-way on the platform and half-way still on the floor). Use the lever again and jump up the jammed platform to the upper level. Destroy the chain and you will be free to go.
Use the turnstile to extend the two pillars on the courtyard, then go further to the right. Use another turnstile to free the path. You'll be attacked by a mysterious warrior. He's quick, but his blows don't deal any damage you. Beat him and it'll turn out that he's a Spartan, Kratos' soldier who came here bearing some bad news.
After a longer scene you'll be fighting another boss, an abomination called Kraken. At the beginning you won't be able to fight, only shout insults towards Zeus. Another cut-scene will commence soon.
Activate Rage of the Titans (L3+R3) and the beast will let go off you. Attack its left tentacle, hitting the visible red scar. When it looses the grip on the pillar, place the dead soldier's body on a raised plate there to activate an air vent. Glide above it to approach the monster's mouth and hit it. Repeat it a few times and Kraken will smash one of its tentacles into the air vent. Grab that tentacle (one of its sides functions like a climbable wall), approach the "knee" and destroy it. Repeat the whole procedure once more, thus cutting off another tentacle. Now attack scars on both tentacles that it's using to hold on to a platform - do that quickly enough and it'll be done for.
Go over the monster's head towards the Phoenix. Grab a Phoenix Feather and a Gorgon Eye, then get on the flaming bird by pressing O.