The Ionian Pyramid

The Pyramid is the name used to a massive alien vessel holding position above the Cradle on Io. Like its counterpart on Luna, this vessel is to be part of the aforementioned fleet that attacked the Sol System during the Collapse, and which is affiliated (or synonymous) with the Darkness. It is possible this vessel may be a Vanguard for the rest of the fleet. Asher Mir theorized that the Pyramid arrived on Io to study the Vex.