Black Fleet

The Pyramids, as they are referred to by the Vanguard, are a massive fleet of Darkness-aligned pyramid-shaped entities. They are the ancient enemy of the Traveler, and were responsible for the Collapse on Earth.

Overview
The Pyramids are closely associated with the Darkness, and are even sometimes referred to as "the Darkness" themselves. However, available information suggests that the Pyramids are nonetheless distinct from the Darkness in a similar way as the Traveler is distinct from the Light. The Pyramids are the ancient enemy of the Traveler, and have actively tracked it through the cosmos for countless eons, bringing destruction to the very civilizations its uplifted either directly or through their agents like the Vex, Hive, or Taken.

The Pyramids vary widely in size, ranging from city-sized "flagships" to smaller but nearly identical vessels closer to the size of a Fallen ketch. They all share a tetrahedral shape, broken up by lines of yellow-orange lights. They are accompanied by fleets of smaller entities known as Pyramid Scales; about the size of a jumpship, these objects are hexahedrons with floating dagger-like extensions extending from their undersurface, and are made of the same chiseled obsidian-like material as the larger Pyramids.

The Ancient Past
The origins of the Pyramids are unknown. They have presumably existed for at least as long as the Traveler; the Books of Sorrow allude to the Darkness laying waste to solar systems, suggesting that the Pyramids may have been active during the rise of the Hive.

Nightmares on Luna
A single, seemingly derelict vessel from this fleet was discovered beneath the surface of Earth's Moon in the years following the Red War. It remains unknown how long this vessel was buried on the Moon, although Eris Morn speculates that it may have been struck down by the Traveler during the Collapse, or left behind intentionally. Its very presence creates Nightmares from the Darkness to haunt the Traveler's Light-bearing Risen.

Multiple Pyramids can be seen in the background when the Guardian receives a vision of the Black Garden from the Unknown Artifact found within the Pyramid on Luna.

Around the time of the Almighty's decent upon The Last City, another Pyramid, one much larger than the one buried on the Moon, had reached Jupiter and made its way towards Io along with its escort fleet of Pyramid Scales.

Arrival
Several days after The Almighty's destruction, the Io Pyramid had touched down near the Cradle. Eris Morn departed for it as soon as it arrived, resulting in Zavala tasking the Guardian to investigate the Pyramid and retrieve Eris.

Trivia

 * The pyramid ship on Luna can be seen from the peak of the Scarlet Keep if you look through the gate that the boss comes through, you may also need to jump to catch a glimpse.


 * When the player encounters the Pyramid of Luna there are two pieces of dialogue that the Ghost can say, what he ends up saying is dependent on what they player has personally done in terms of narrative. On one hand he will say that he does not recognize the ship, but on the other hand he will say that he does recognize it and even notes the impossibility of it being there.
 * Ghost Quote 1: "What... is that? I've never seen anything like it."
 * Ghost Quote 2: "That's... one of those Pyramids. It can't be. That should not be here."