From Destinypedia, the Destiny wiki
Pyramid Scales are entities deployed by the Pyramids. They have been observed on Io, where they inject Darkness into regions of Echo Mesa to undo the Traveler's work, as well as on various other worlds visited by the Pyramids and in the Black Garden.
Pyramid Scales seem to be essentially miniature Pyramids, being about the size of a jumpship. Unlike their larger counterparts, which are simple tetrahedrons, Pyramid Scales are hexahedrons with a projecting tetrahedral extension hovering below their underside. They were first sighted over the Echo Mesa on Io, empowering the enemies of humanity that flock towards them and reap of their paracausal power. Pyramid Scales also begin the Contact Activity, in which Guardians must fight to contain their Darkness in Gambit fashion; by killing the enemies that drop Dark Motes, containing them in the nearby Bank and ridding any Taken Blockers sent by Quria, Blade Transform.
Weeks following the arrival of the Io Pyramid, it began deploying Pyramid Scales out in force to actively patrol and survey its surface, likely for terraforming purposes. Other Pyramid Scales were reported on other planets including Mercury, Mars, and Titan; the later which Guardians fought to contain their Darkness much like at Io.