Kieran Halcyon was a Jedi Knight during a golden age of the Old Republic, four centuries before the rise of the Empire and Emperor Palpatine. Kieran was part of the legendary Halcyon line hailing from the planet of Corellia, ancestor to Nejaa Halcyon and Corran Horn. Kieran was one of the first Jedi Knights to experiment with a dual-phase lightsaber, adding the ability to extend his blade to almost three times its normal length. Like all Jedi stemming from the Halcyon bloodline, Kieran was a Jedi Knight with a very low telekinetic ability, but with a very high sense and alter ability, as well as the skill to absorb and redirect energy, also common among all Halcyon Jedi.

During Kieran's time as a Jedi Knight, Corellia faced the problem of dealing with the terrorist Afarathu sect. This organization was made up of Selonians who called for an end to human domination of the Corellian government and used terrorist methods to coerce the Corellian government into giving them the political power. Attacking government buildings, ships, and workers, the Afarathu sect managed to amount an impressive death toll. Innocent Selonians were becoming targets of attack for those who generalized their hatred of the Afarthu sect.

The Jedi Council knew intervention was necessary but feared having Corellian Jedi deal with the problem would create a conflict of interest in the Jedi assigned to the task, and feared emotion might distract any Corellian Jedi from finding a peaceful solution. Most Corellian Knights, Kieran included, agreed, although somewhat bitterly. Instead of tracking down terrorist, the Corellian Knights were asked simply to keep order in the system while other Knights were assigned to the task of investigation and hunting down suspected terrorists. However, not all Knights followed the Council's orders. Recently commissioned and young Jedi Knights conducted unauthorized searches which resulted in the death of no less than four Jedi.