The Eirae

(The Eirae may refer to the species, or the one specific Eirae who is relevant to the plot)

The Eirae is the name of the rift creatures that are used by the Astorissian Conquest to summon people to the training facilities. It has strong psychic capabilities and can travel immense distances almost instantly via the rift. It is referred to as Geshekra in an old Byzahren myth. On Earth, human documents mention an "Astral Chronogoose" fitting the description of the Eirae. Of the species who have encountered it, only the Cromsidians know it (them? more than one probably?) as the Eirae, the name it calls itself, due to their psychic abilities.

In the war
Tordronites managed to enslave (many?) Eirae. They force it to summon beings from across the galaxy. This is a random process, with a few restrictions. Only species capable of surviving the atmosphere and suitable for combat are summoned, and the rate at which each is summoned maintains good ratios of species that can be assigned as frontline, agile, and supportive soldiers.

Role in Story
The specific one of the Eirae that summons the protagonists is kept caged underground below Fort Raimar. During the uprising there, the squad find and free it, and in return it takes them to Estevahl's home. It later returns and takes them to Lokras' camp, and (probably) is their method of infiltrating the next fort where they free all those that were captured after Fort Raimar.