You'll eventually reach a circular hallway. Go right and head through the first passage you see. Get through the traps and you should reach a room with Undead Archers and a pool of water replacing a large portion of the floor. Kill the archers and pull the lever at the end of the room, then head back to the hall and use the newly-descended crank to shift the rings. Keep turning the crank until you reach a room with what looks like a large barrier. Walk up to the barrier to trigger a cutscene in which Kratos obtains the Blade of Artemis. Hold and simultaneously to switch from the Blades of Chaos to the Blade of Artemis at any moment. Progress down the path and make your way to the Challenge of Atlas.
and 
simultaneously to switch from the Blades of Chaos to the Blade of Artemis at any moment. Progress down the path and make your way to the Challenge of Atlas.