A Delta Quadrant society of covert observers who surveyed Voyager from afar, only to be fooled by the Doctor's daydreams.
The Hierarchy is a Delta Quadrant civilization that gathers information on other ships through covert long-range surveillance, assessing targets before deciding whether to attack. Its people have large, bulbous heads, and their culture is rigidly ruled by superiors.
A low-ranking Hierarchy observer named Phlox tapped into the Doctor's subroutines and mistook the hologram's fantasies of commanding Voyager for real events. Janeway seized on the misunderstanding and had the Doctor play the role of an Emergency Command Hologram to scare the Hierarchy off, in Tinker, Tenor, Doctor, Spy.