Cix-Tu

The Cix-Tu are an alien civilization in the Covenant's peripheries on the trailing side of the Orion Arm. They are a minor power at best, with a very limited presence in the Holy Ecumene, and so they're mostly known through legend and rumor. They are infamous for their brutality, and for their accomplishments in the medical field. It is said that a Cix-Tu surgeon is the finest that money can buy, though their clients would prefer not to think about how that expertise was trained. As they both maintain an independent empire and semi-regularly deal with the Covenant, they occupy a hazy borderline between Ulterior and Fringe status.

Their legendary brutality originates from the Cix-Tu Empire's slavetaking operations. To the worlds of the Marrak Frond and the Hrelon Delve, they are a persistent and dire threat. Whole cities and small colonies have been depopulated by slaver fleets. Millions have been taken to be sold as chattel elsewhere in the galaxy, or worse.

Biology
Physically, the Cix-Tu are unremarkable. They are tall humanoids with pale or sallow skin and slender limbs, a combination which often invites comparison to a cross between a Kig-Yar and the San'Shyuum. Although more than capable of surviving high G-loads, the Cix-Tu physiology seems to be adapted to low gravity. Indeed, their starships often run with less than half of Earth-standard gravity, and Cix-Tu soldiers are excellent zero-G combatants.

Perhaps their most notable features are their eyes. Cix-Tu have three eyes with reddish sclera and narrow pupils. At the opposite end of their skulls is a small 'tail' of tissue, generally no longer than 20 centimeters. The tail appears to be a vestigial organ, left over from an earlier epoch in their evolutionary tree. Cix-Tu beliefs hold that the tail contains important nerve bundles, and by piercing this tail they can improve their eyesight or sensory acuity. On the other hand, many lower-caste Cix-Tu have their headtails cut off at birth, and suffer no ill-effect from the procedure.

An interesting quirk of Cix-Tu biochemistry is that their bodies do not use chemical hormones to regulate their bodily functions. Instead, they cultivate an ecology of viral agents, the exact makeup of which is unique to each individual. Replicating this viral ecology in a lab is nearly impossible, and organ cloning technology is one that the Cix-Tu do not seem to have developed.

History
The Cix-Tu were a mystery in many ways to the Covenant, starting from the time of their first encounter in the 20th Age of Discovery, and continuing for many centuries hence.

In some ways, the Cix-Tu are a puzzle to the Covenant. Their technology is a hodge-podge of machinery bought or stolen from other spacefaring civilizations, as well as very advanced homegrown cybernetics. Their biology is largely unstudied, because Cix-Tu slavers and soldiers alike have a fanatical dedication to retrieving the bodies of their fallen comrades. Their religion is arcane and sparse, and has little to do with the Forerunners. Both their slaver fleets and their military seem to be controlled by the same government, the Imperial Directorate of their homeworld.

After the initial encounters with slaver fleets, the Covenant response to the Cix-Tu threat has been to beef up patrols along the Sullen Sea, and to purchase back enslaved Covenant citizens. There has been no talk of invading Cix-Tu territory, because they are thought to be a useful buffer against whatever empire lies beyond. This changed during the 22nd Age of Doubt in 2367, when a Cix-Tu fleet pushed into Covenant territory and begged for political asylum. This is when the full truth of Cix-Tu civilization was revealed to the galaxy outside.

This makes cloning organs nearly impossible, even in laboratory conditions. It also means that autoimmune diseases are endemic to Cix-Tu. Their median lifespan is thirty-five years. Bionic transplants can push this to forty-three years. Centuries of genetic engineering and gene therapy development has pushed the median lifespan to fifty-one years. With organ transplants, Cix-Tu lifespan can be pushed to nearly a hundred years.

The Imperial Directorate maintains control over Cix-Tu civilization, because they control who has access to the organ banks, and who gets fed into them. Upstanding Cix-Tu citizens are kept alive with organs taken from criminals and political prisoners. Criminal Cix-Tu, even minor ones like embezzlers and chronic traffic violators, are sentenced to death and broken up for spare parts.

High Charity came this close to launching a humanitarian mission to put down the Imperial Directorate and liberate the Cix-Tu civilization, but then much of the fleet was diverted to ending a civil war in the Solis Nexus, and the rest were sent to a border skirmish with the Jiralhanae. The Cix-Tu threat fell to the backburner of Covenant politics, and then was all but forgotten. The Imperial Directorate slowed down slavetaking operations in Covenant territory, instead tasking military and slavetaking fleets alike with long-range patrols. Many Cix-Tu ships have been spotted prowling the worlds of the Ulannon Migration and the periphery of the Orion Complex, and may have made it as far as the Human Sphere. Thus far, their goals are unknown.

As many as five million Cix-Tu refugees have settled within the Holy Ecumene and somewhat integrated into Covenant society.

Trivia
By a strange quirk of fate, the Cix-Tu word for 'Doctor' is a near-homophone with the Pan-Sangheili word for "Harvester". This coincidence greatly annoys one surgeon residing in the Shoal. He's an ophthalmologist, not a Harvester of Eyes, and you'd better not call him that to his face.