From the Book's Opening Paragraph:
Welcome to "Descent," the seventh installment of the Gloria Mundi chronicle for Mage: The Awakening. In this story, the characters discover Adam's fate (he has been murdered by fanatical apostate mages known as Banishers) and descend into a dangerous, but potentially enlightening, realm. That realm is an ancient Atlantean temple and cache of knowledge known as the Obsidian Palace, which was planted by the Mysterium and designed for use by mages of the Moros Path. For many years, the entrance to the Palace has been hidden by a mausoleum in a graveyard near the cabal's hallow, but its location is only revealed to the characters after Adam's murderers try (and fail) to gain access to its secrets. To further complicate matters, Adam’s goetic Pride-spirit appears to Morrigan and tries to sabotage her efforts. If Morrigan can let go of her self-importance and ambition, the characters have a chance to defeat the Pridespirit. If not, the whole cabal faces the consequences.