The Massive is the appropriately-named giant flagship of the Irken Armada, and is escorted by many great ships at all times, except in the episodes Backseat Drivers from Beyond the Stars, where the Massive was dragged away from its fleet through a hacking by Zim; and The Nightmare Begins, in the ending where Zim reported in to the Almighty Tallest.
As the lead ship of the Armada, the Massive is constantly occupied by the two leaders of the Irken Empire, the Almighty Tallest. From the bridge, they monitor all of the machinations of Operation Impending Doom II. The main chamber, where Almighty Tallest Red and Purple spend most of their time, is equipped with a large screen and with a long-distance communication system, which the numerous Invaders and Zim himself make use of, contacting the Tallest to inform them of their progress in conquering their respective planets. The frigate is run by the Navigators, who are also in charge of communications.