Planet of Origin: Kirish, a large planetoid, several time the size of a regular tellurian world. It has a solid core, cold temperature, extremely high gravitic constant, and an atmosphere so thick as to be almost liquid.
Kirishiak are an advanced aggressive species that developed into a space faring civilisation over a million years ago. They were the youngest of a group of civilisations that included the Walkers, the Shadows, the Vorlons, the Torvalus, the Triad and the Mindriders. They started as an expansionist power but after defeat at the hands of their elders, turend toward a more humble approach.Kirishiac are huge bipedal creatures with multiple redundant cardiopulmonary systems and cells arranged in complex lattice structures. They stand over seven meter tall and are almost translucent. They have eight hearts spread throughout their bodies in order to pump blood through limbs on their high gravity homeworld. This redundancy and the necessary strength of their physiological systems made them highly resistant to most kinetic attacks.
Once under a united feudalistic government, they started to wander into space and conquered all nearby systems, using heavily armed spaceship and protecting their physical being in atmosphere suits able to reproduce the gravity and pressure of the home world. For several thousand years, they expanded their empire, sometimes wiping out a young race, but most times forcing them into slavery. When they discovered hyperspace, they wandered in the territories of older species such as the Walkers and the Shadows. This brought them in a direct if short war with much older civilisations and they were beaten back to their homeworlds. They later opened communication channels with those older races to be granted access back into space.
Source: Babylon 5 universe. Babylon Wars Sourcebook.