The Dominion of the Celestials and Makuta was a very large, loosely defined political region of space that existed between 100,000 BBY and 49,000 BBY . It covered much of the western half of the galaxy, and also some regions to the far north and north-east of the galaxy that were outside of the League of the Six Kingdoms . Much of this territory would later become the unknown regions. This region was under the direct control of the Order of Mata Nui, and patrolled by the Makuta . The celestials carried out many experiments here, and it is unknown to what extent the unknown regions was affected by their presence.
The celestials also created the border between the Dominion and the League of the Six Kingdoms, which consisted of a Hyperspace abnormality that would impair travel between the Galactic east and west for tens of millenia to come.
After the successful Makuta/Human rebellion and the destruction of the celestial worldships at Vitea , the Dominion was dissolved.