Deep in the Osirian desert stands the blank-faced monument known as the Sightless Sphinx. In search of the stolen mummy of Chisisek, the architect of the flying tomb of the Sky Pharaoh Hakotep I, Ezren, Harsk, Merisiel and Valeros track the cult of the Forgotten Pharaoh to its secret headquarters inside the sphinx. There they confront monstrous mercenaries and servants of the demon lord Areshkagal before finally confronting the masked cultists and their leader, the Forgotten Pharaoh, who has been possessed by a fragment of Hakotep's soul.
Secrets of the Sphinx helps propel this storyline forward as our heroes descend into the Sightless Sphinx to confront the Forgotten Pharaoh and his evil cult. Ezren, Harsk, Merisiel and Valeros band together once more to try to save Wati and its people; we see some discord in the group due to the mask and I enjoyed that change-up in their dynamic. The antagonists feel one-note; but the Egyptian fantasy setting helps them stand out. If you've been enjoying the series so far but feel the last two entries have muddled around a bit, Secrets of the Sphinx moves the plot forward and set up a very epic part five.