Hellhound (Cosmic Engineers)

The Hellhounds (a name given to them by the Engineers) are a hostile alien species hailing from an unknown galaxy.

Biology
Physically, they're reptilian beings with a heavy constitution, described as a combination of alligator and grizzly bear. Their mentality is entirely based on the idea of the collective, to the point that individuals are willing to sacrifice themselves and others if that will result in victory for their species.

History
For over a million years the Hellhounds have waged war against the Engineers, hoping to find a way to defeat their enemies and assume control of the universe. While both races' technology has been evenly matched in terms of military combat, the Hellhounds alone have developed ships that allowed them to traverse the space between two universes.

In the year 6948, when it was found that our universe was going to collide with another (resulting in the annihilation of both), the Hellhounds took the opportunity and planned to foil the Engineers' attempts to prevent the collision. Even though most of the Hellhounds would perish along with their enemies in the ensuing destruction, the race itself would still survive thanks to the few who would be able to escape, and who planned to return and recolonize what was left after the universe recovered.

Appearances

 * Cosmic Engineers, by Clifford D. Simak (1939)