The Jjarowere an extremely advanced species--or an extremely advanced individual--which vanished from the Milky Way galaxy millions of years before the battle of Tau Ceti, leaving much of their technology to fall into the hands of the Pfhor. The Jjaro possessed high-quality cyborg technology, such as that used to create the S'pht, as well as a star-destroying weapon known as the trih xeem, the ability to move entire planets by warping space around them as was used by the S'pht'Kr, some sort of time manipulation technology, and various ways of dealing with the W'rkncacnter.
List of Jjaro Ships
- The Jjaro were first used in an earlier Bungie game, Pathways Into Darkness, as were the W'rkncacnter.
- When viewing the level Never Burn Money in a map editor, text can be read that says "JJARO WERE AT TAU CETI," possibly even at the battle fought by the Cyborg in Marathon.
- Many concepts of the Jjaro were made into the Forerunners in Halo, a later Bungie game.