Callisto told Kratos he needed to find the Skull of Keres in the Temple of Ares in Sparta in order to enter Death's Domain. Kratos reached the Temple of Ares and found a mirror inside, showing him free of his chains.
The reflection then tried to grab Kratos and pull him inside the mirror, but failed. The mirror then sent out an image in the form of his younger self to attack Kratos. Kratos then grabbed the image and threw it at the mirror, shattering it. Kratos then tackled the image into the mirror, breaking it, and revealing the Skull of Keres. He then returned to Atlantis using The Skull of Keres to enter the Domain of Death and save his brother.