Huragok

Engineers, called Huragok in the Forerunner language, are the only known non-combatant race of the Covenant.

Summary
While the Prophets guide, direct and manage Forerunner research, it is the Engineer caste who must excavate, unlock and transport Forerunner artifacts. These remarkable aliens are patient, almost completely silent and utterly focused on their task and its religious implications.

Their concentration has been described as "a trance-like reverie" by the few who have witnessed it. They communicate only with Prophets - a fact that may contribute to the balance of power between Elites and Prophets - and will usually ignore anything that is neither a Prophet nor a Forerunner artifact, although they seem to have a general interest in all machines. One observed exception is a high-pitched, keening wail that Engineers will emit should Forerunner objects or structures be threatened.

Some Engineers are used to help construct and repair the Covenant starships from the inside, in conjunction with the Drones who construct and repair the ships in space on the outside.

Engineer Anatomy and Physiology
The Engineers are an amorphous, purple-skinned species that float using gas-bladders, even continuing to float when dead. They have six dark eyes and 4 tentacles that can split into very small, near-microscopic cilia. The Engineers use these cilia to construct, repair, or rebuild nearly anything they can grasp. They can take apart whole vehicles and rearrange the entire structure of it in a matter of seconds, and it will still operate. They learn at an unprecedented rate, and store that information for future reference if ever they need to repair the same thing twice.

Engineers are not a tactical threat and are hardly ever seen in combat situations. Engineers do not regard humans as enemies. Engineers even aided the Master Chief by repairing his shield generator of his MJOLNIR armor in the novel Halo: First Strike. This Engineer also had repaired a broken Needler the Master Chief was using. After repairing the Armor a marine killed the engineer, stating that it had learned all about the MJOLNIR technology and could not be allowed to relay said information.

The blood coloration of the Engineers looks a deep scarlet orange. Piles of Engineer gore can be seen in the Halo Graphic Novel, whereupon the squad of Elites come across them inside the ship Infinite Succor. The blood also looks highly viscous and sticky. However, it is possible that this is not entirely accurate, as the Graphic Novel took several liberties with appearances.

The Engineers' relationship with the Forerunner
All of the following information was discovered in the leaked Limited Edition Beastiarum, courtesy Mocambo

The Engineers (Huragok) were created by the Forerunner prior to the first Activation. They survived the Activation and were collected by the Prophets from various M-Series facilities. They possess no true tissue or organs. Given sufficient raw materials, a pair of Huragok can produce a unified replica of themselves in approximately 45 minutes. A maximum of three Huragok may participate in the reproduction event, the subsequent time for creation of an offspring is cut down to 30 minutes.

Appearances
Engineers feature in Halo: The Fall of Reach, Halo: First Strike and Halo: Ghosts of Onyx.

In Halo: The Fall of Reach, an Engineer is observed by the Master Chief dismantling and re-assembling a human car on Sigma Octanus IV. This was their first recorded appearance by the UNSC.

In the Halo Graphic Novel it is noted that some engineers were stationed on the Infinite Succor. Rtas 'Vadumee noted that the Flood had killed Huragok, smearing their blood onto the floor. In Halo: First Strike, an Engineer repaired the Master Chief's Needler, then later his Energy Shield and was later shot by Lieutenant Haverson, because it presented the risk of divulging the MJOLNIR's improved shield design to the Covenant. Haverson appeared to feel some pity for the creature.

Engineers were originally intended to appear in Halo 1, but due to time constraint issues, Engineers were "left on the cutting room floor." But they were not deleted entirely from the software, and modders have since located the Engineer files on the game disc and spawned Engineers in various configurations, hence the images that may be found. Other than this, Covenant Engineers are never seen throughout both games.