The battle with Atropos and Lahkesis. You have Atropos trapped in the mirror now so she won't cause any more trouble. Now, when Lahkesis goes down like that (trying to catch her breath) use the Amulet of the fates to slow down time and find the mirror Atropos is in. Attack her as much as possible when time resumes- eventually the mirror will shatter. Keep doing this until one mirror is left.
Once things are down to one mirror Lahkesis stands in front of it to protect it. Atropos is completely out of the picture at this point. Lahkesis has some new attacks- when she unleashes the energy pillars stand between them to avoid them. She'll fire more energy shots as well- deflect these.
Lay some Cronos' Orbs around her and attack from mid range. Eventually she will fall and have an icon over her head. Hit the circle button to trigger the action sequence, which goes like this:
Kratos leans toward her and picks up her staff then [LEANS BACK] and hits her on the back with it while she tries to get up. Kratos picks her up and throws her to the middle of the room. Atropos crawls out from the mirror behind Kratos and grabs him. Lahkesis recovers then readies her staff. Kratos [NOTICES] the attack and quickly breaks out of Atropos' grip and grapples to the side grapple point as Lahkesis flies toward Atropos and stabs her with the staff. Kratos [SWINGS] toward Lahkesis and grabs her then holds her and [STABS] her directly in the forehead with his blade. Kratos pulls out his blade then pushes her into the mirror to join her sister.
At this point the battle is over- they are both trapped. To finish it shatter the mirror.