The Vagaari Empire was nomadic in nature, yet controlled a large area of the Unknown Regions.
They were enemies of the Chiss Ascendancy, yet official Chiss policy never officially labeled them as so. Vagaari began moving through Chiss space around 37 BBY. A large number of them were destroyed by Thrawn at the destruction of the Outbound Flight. After that they retreated to their own corner of the Unknown Regions, recovering from their losses and building up forces for an eventual attack on the Chiss. The Chiss were aware of this buildup, and feared that they had "already made alliances with powers even more dangerous than they are," presumably the Far-Outsiders.