Hrangans

Humanity's great enemy during the Double War, the Hrangans were perhaps the most alien sentients ever encountered. Their social system was structured on the basis of a number of biological castes, most of whom seemed to belong to different species, so different were they. Of the Hrangan millions, only the so-called Minds were truly intelligent, and humanity never communicated successfully even with them. The Hrangans were bitterly xenophobic; prior to the Double War, they had enslaved a dozen less-advanced races, and there is evidence that they had exterminated others entirely. Hrangan slaveraces include:

Hruun
Often used in combat during the Double War. The Hruun were more intelligent than most other Hrangan slaves. Their homeworld was a heavy-gravity planet by human standards, so the Hruun were warriors of immense strength. Among their other attributes was an ability to see well into the infrared that made them especially suited for nocturnal combat.

Githyanki
Often termed soulsucks by humans. Barely sentient, malevolent, and potent telepaths, the Githyanki were capable of bending and twisting human minds, sending false visions, hallucinations, and dreams, strengthening the animal side of man and warping judgement and reason, all for the end of turning brother against sister.

Dactyloids
Human term for a winged Hrangan slave-race employed as shock troops during the Double War, given to the creatures because of their vague likeness to pterodactyls of Old Earth pre-history. Dactyloids were savage, but small-brained and only semi-sentient.

The war effectively destroyed the Hrangans, except on Old Hranga itself and a handful of their oldest colonies.

Quotes about the Hrangans
In The Hero, which is set during the Hrangan Conflict, Major Grady describes Hrangans as: "'A real enemy. Like us, they've had a professional army for generations upon generations. They're soldiers, born and bred. Good ones, too. They've got screens and modern weapons. They'll be foes to give our assault squads a real test.'"In the introduction to Nightflyers, Royd Eris states that:"'By the time the stardrive had transformed the Federated Nations of Earth into the Federal Empire, the Volcryn had moved into the fringes of Hrangan space. The Hrangans never knew it. Like us they were children of the small bright worlds that circled their scattered suns, with little interest and less knowledge of the things that moved in the gulfs between.'"In And Seven Times Never Kill Man!, Proctor Wyatt of the Steel Angels reads the following passage from the "Chapter of Teaching":"'In those days much evil had come upon the seed of Earth, for the children of Bakkalon had abandoned Him to bow to softer gods. So their skies grew dark and upon them from above came the Sons of Hranga with red eyes and demon teeth, and upon them from below came the vast Horde of Fyndii like a cloud of locusts that blotted out the stars. And the worlds flamed, and the children cried out, 'Save us! Save us!"Also in An Seven Times Never Kill Man!'', the Steel Angels' weaponsmaster C'ara DaHan confesses fears to Proctor Wyatt about his prophecies:"'There is a tale, my Proctor—one that troubles me. Once, it is said, in the long centuries of war, the Sons of Hranga loosed upon the seed of Earth foul vampires of the mind, the creatures men called soul-feeds. Their touch was invisible, but it crept across kilometres, farther than a man could see, farther than a laser could fire, and it brought madness. Visions, my Proctor, visions! False gods and foolish plans were put in the minds of men, and...'"Proctor Wyatt, when accused of allowing the Jaenshi of worshipping Bakkalon, he responds:"'You wonder whether I commit the First Fallacy, remembering perhaps the Sacrilege of G'hra when a captive Hrangan bowed to Bakkalon to save himself from an animal's death, and the False Proctor Gibrone proclaimed that all who worship the pale child must have souls.'"In The Stone City, the elderly space pilot Cain tells Holt that he's been to Old Hranga, adding that:"'They say there are still some Minds on Hranga, deep underground, waiting to come back and attack the manrealm again. But all I ever saw was a lot of kill-castes and workers and the other lesser types.”"Also in The Stone City, while exploring the mysterious subterranean tunnels of the city, Holt discovers an open doorway. Beyond it, he sees what he thinks is a Hrangan structure, describing:"'A mountain ledge overlooking a hard arid land, a plain of baked brick broken by a great crevasse. A city stood in the center of the desolation, its walls chalk white, its buildings all right angles. It was quite dead, but Holt still knew it, somehow. Often Cain narKarmian had told him how the Hrangans build their cities, in the war-torn reaches between Old Earth and the Fringe.'" In A Song for Lya, the telepath Robb describes Hrangans as having "sour minds, rank with hate and bitterness, and I feel unclean when I come out." He also mentions that Hrangans practiced ritual cannibalism.