"ONE HUNDRED THOUSAND YEARS AGO, the galaxy was populated by a great variety of beings. But one species—eons beyond all the others in both technology and knowledge—achieved dominance. They ruled in peace but met opposition with quick and brutal effectiveness. They were the Forerunners—the keepers of the Mantle, the next stage of life in the Universe's Living Time. And then they vanished. This is their story."—Jacket description
The book takes place during the time of the Forerunners, the ancient race that built the Halo rings encountered in the games.
- A.I. Is a Crapshoot: Mendicant Bias turns rampant, sides with the Flood, and declares war on his creators.
- Somewhat true, Mendicant Bias was in charge of a Halo when the Forerunners were first testing them. When it was used on a precurser world it broke the cage of the timless one. The timeless one presumably caused the corruption of Mendicant Bias.
- Action Girl: Glory of a Far Dawn.
- Awesome McCoolname: Forerunners, being the pompous, overbearing pricks they sometimes are, usually have such names. Bornstellar Makes Eternal Lasting, Splendid Dust of Ancient Suns and Glory of a Far Dawn, to name a few.
- There seems to be 3 different ways to name Forerunners. The first is the "descriptive" names above. The second seems to be names derived from one of their dead/ ancient languages (The Master Builder is named Faber (craftsman in Latin), a lifeworker is named Calyx (part of a flower), etc.). The third are unofficial titles that have become their using names; the Didact got his name while teaching at a War College, and he's known only as such from then on.
- Batman Gambit: The Librarian's plan to reunite with her husband involved millennial genetic commands given to humans, a self-constructing ship hidden under a mountain, and calling favors from multiple Forerunner officials over a thousand years.
- BFG: The Halo rings.
- Big Bad: Faber, the Master Builder. He not only commissioned the Halo Array in the first place, but he's also an all-around jerk, and whenever he shows up in a star system it's generally bad news bears.
- Bigger Bad: The Flood.
- Also, the Timeless One.
- Cool Ship: The Didact's Planet-Breaker.
- Eldritch Abomination: The Flood, although they're only briefly mentioned.
- Also, the Timeless One. When a group of humans attempt to communicate with it, it tells them things so horrifying that they promptly lose their minds and commit suicide.
- Fantastic Racism: Forerunners toward... well, everybody who isn't a Forerunner. Bornstellar mentions that his teachers told him humans were not much more than animals (which he disagrees with upon meeting some). The Master Builder calls a San'Shyuum a "dirt beast", the "most obscene slur for someone not of [their] race".
- Heck, their racism extends even within their own race. Nobody likes or respects the Warrior-Servants because the Mantle stresses pacifism (ironically, Warriors are shown to be the most devout and honorable followers of the doctrine). The Master Builder especially; he probably considers his rate of Forerunner the only really worthy one.
- Final Battle: Also the largest-scale battle scene in the series.
- Go Mad From the Isolation: Heavily implied with the Confirmer. Halo really loves this trope.
- I Know Your True Name: The Didact's consciousness within Bornstellar tries this with Mendicant Bias, to the letter.
- Insignificant Little Blue Planet: "This station was located on the system's third planet, known as Erde-Tyrene: a forsaken place, obscure, sequestered, and both the origin and final repository of the last of a degraded species called human."
- Rebellious Spirit: Bornstellar Makes Eternal Lasting in the beginning.
- The Precursors: The Forerunners are preceded by an older, even more highly advanced race called - you guessed it - the Precursors.
- The Forerunners themselves are viewed the same way by other alien civilizations in the modern day.
- Fun fact: the name "Forerunner" is not, as you might expect, a Translation Convention based on the name humans and Covenant use for them; it's actually a close translation of the species' name for themselves, and Bornstellar even notes that it implies that they are merely a stepping stone towards something else, and perhaps better.
- Sealed Badass in a Can: The Didact is found by Bornstellar inside of a Cryptum, or sarcophagus, where he has been hibernating for thousands of years.
- Sealed Evil in a Can: The Timeless One. Also, the backstory for the Flood seems to involve ancient ships containing canisters full of dust-like proteins which seemed benign and even useful at first.
- The Obi-Wan: The Didact acts as a mentor to Bornstellar, the protagonist, and they travel together throughout most of the book.
- The Reveal: The very nature and setting of the story makes these commonplace. Though some big ones are dropped near the beginning rather casually with little drama surrounding them, there are many universe-changing ones. First among them seems to be the revelation about the ancient human empire that existed contemporary to the late Forerunners.
- A particularly big one is in the very end:
"We meet again, young one. I am the last of those who gave you breath and shape and form, millions of years ago. I am the last of those your kind rose up against and ruthlessly destroyed. I am the last Precursor. And our answer is at hand."
- Translation Convention: This is actually explained in the beginning of the book, where all terms and idioms are said to have been translated to understandable words.