The Summary of the first book as far as what you need to know (NOT very in-depth)
Now that you have had a brief introduction into the Forerunner way of life, its time to start with the synopsis.
So Cryptum starts out with a young Manipular from the class builder, who had been exiled to a new family on what we can assume to be mars, consisting of Miners. the Reason this Manipular had been sent to a new family, was because he repeatably defiled his father, instead of wishing to achieve his evolution, he sought out adventure instead, he actually even attempted to sneak out from his fathers grasp and go on one. he was caught, so his father decided it was good for him to be placed with a miner family until he learned discipline. but, the Manipular escaped from that families grasp and got onto a supply ship heading to the neighbor planet named Erde-Tirenne, which we can safely assume is Earth. he was told by his ancilla that the great adventure he was yerning for would take place on this planet, at the time, we do not know this, but the ancilla was a special one, programmed by the main LifeWorker, known as the Librarian, who was behind the great journey by all life that was about to take place.
The Manipular Reaches earth and quickly finds humans to help him on his journey. Chakas, a *normal* human, whom was biologically very similar to the average human today, and a thief, very untrusting of all of those around him, but eager to earn money. and Riser, his best friend the one who took him in and taught him how to be an honest man, who was very smart and funny, a Florian a race that is a midget form of humans, with dull facial features, but lives for a few hundred years. these men take him across a lake known as dmankajin crater, to a vault of LifeWorkers said to hold an artifact of the Forerunners. while crossing the lake, which was flooded by creatures known as Merse, whom remained calm only if pleased by a travelers music, started to become uneasy, not happy with the music they had been playing, but the humans speed up the boat and make it across safely. while there, the Humans' Gaea, an ancient human spirit implanted in all de-evolved humans at birth, activate and guide the Manipular to a tomb or Cryptum , instead of the temple in which he wished to go, interested in the new adventure in front of him, the Manipular enters the Cryptum to find lifeless statues inside, after progressing further, he is confronted by a voice, asking him if he wishes to raise the Diadact out of his slumber, the former head of the warrior servants during the great war *destroyer of humans*. at his peek of interest the Manipular decides to awaken the Diadact as he nurses him back to health over a the next week. now in his health, the island senses the Diadact's presence and awakens, causing the center mountain of the island to seemingly disappear, and be replaced by a sphere being constructed, as the sphere nears completion the miner family finds the Manipular, but is too late, when the Diadact teleports him, Chakas, and riser onto the ship, and the go off into space. as the Diadact was in a great slumber for several centuries, due to his exile from the horrible tactics he used in the great war, he did not know what had happened since. their first stop was Charrum Hakkur, the final battle of the great war, ruins, this was surprising because the planet was the original home of the precursors, with architecture that even Forerunners couldn't destroy. while there the Diadact visited the time lock, a device that humans used to contain the last precursor. the device was broken and the precursor was gone, a foreshadowing of what is too become. meanwhile the human's Gaea's come to the surface, and the humans now have two voices in their heads instead of one, which are slowly informing them of everything that happened. The humans continue their journey though the universe, as the Manipular has a forced evolution, where he first picks his name 'Bornstellar Makes Eternal Lasting', taking an imprint from the Diadact, he continues to become the new role of the Diadact and becomes separated from the humans. what happens to them is unknown. afterwards the Forerunners spread into chaos, as the master builder (the leader) betrays the mantle and turns the halos on them to ensure his rule.

That's it for the Summary, that all you need to understand to know what is happening in the second, but I still recommend that you read this book, to get the full story, as well as the rest of the series for a great story.