Defiance of the Fall

1. Zac refuses to abandon Zecia and plans to find the ancient Centurion Base, hidden in enemy territory, and use its weapons against the cult. He learns of Foreign God weapons deep in the Kan'Tanu sector, with about three years left before the Left Imperial Palace opens. The System gives him a final Flamebearer quest that requires activating them.
2. The Undead Empire sends Kator along. Zac combines the mission with a rescue of Vilari. Kator's private plans, a civil war in the Undead Empire, and several Sealbearers from stronger sectors trapped in unstable space complicate the trip.
3. A report on rival Flamebearer candidates (Ch 1,208) names Kaltosa Lu, a descendant of the Centigrade Pryer, a Holy Daughter of an Insectoid species, and Eouso from the Pesvati Rift in the Eternal Storm. Zac credits his recovery speed to his Sindris heritage (Ch 1,212).
4. Reviewers say Zac finishes the Shard of Creation and Oblivion storyline and uses its four rewards to survive an ambush and advance his Dao. He then spends a month fighting to survive, gains a crew and a new imperial ship, and loots ancient artifacts. He also survives a high-stakes trial that draws the interest of several great houses.
5. The wiki records the Empire claiming worlds (a dozen E-grade and two Early D-grade) to test how the System's shroud works (Ch 1,227), and Vilari infiltrating scouting targets (Ch 1,249). Zac fights a Peak D-grade pugilist who must have been force-raised by ritual (Ch 1,239).
6. The Buddhist Sangha attacks and tries to capture Zac and fails, nearly bringing Zecia to its knees. Thea Marshall escapes the Buddhists. A civil war splits the Undead Empire, the Primo is cut off, and the Reavers cannot decide whether to kill Zac. Zac meets the Terminus Council, and he and Kator are briefly pulled into the hells.
7. A forced truce between Zac and an antagonist takes up much of the book, followed by a final battle that spans over a dozen chapters with several reversals. Zac wins narrow victories against foes at or just above his level, including half-step and full Monarchs.
8. Book 16's publisher blurb opens with the Kan'Tanu leader dead, the Eternal Guardians unleashed on the cult, and Zac wounded and worn out after a betrayal, having survived the Imperial Graveyard. We read that as this book's ending.

Zac emerges from the Imperial Graveyard having killed the Kan'Tanu leader and loosed the Eternal Guardians on the cult, but a betrayal has left him wounded and exhausted. Book 16 starts there, with the Ultom Courts competition about to begin.

Middle D-grade (Hegemon). Level 175 is the last wiki-recorded value (Ch 1,184). His level and grade at the end of Book 15 are not confirmed. A reviewer expects him to reach C-grade within a book or two.