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Lieutenant Commander Michael Pomare, Office of Naval Intelligence, UNSCDF Navy
ONI Seal 1
Thanatos-Class Prowler
Production information



Stealth Corvette



Technical specifications
Slipspace Drive

Shaw-Fujikawa Translight Engine

Slipspace velocity

2.625 lightyears per day

  • Active camouflage emitters
  • Stealth ablative material
  • Internal thermal/radiation sinks
Sensor systems
  • LDAR
  • High-resolution visual optics
  • Infrared visual optics

18 x JANUS Drone Countermeasures









Year introduced


  • Human-Covenant War
  • Great Schism
  • War of Vengeance



Successful reverse-engineering of Covenant technology has been difficult for the UNSC, primarily because of the Covenant's own poor understanding of the technologies they use. Human researchers often don't know if the applications to which the Covenant put their equipment were the original intent of its originators, the Forerunners, and a good deal of research has been simply guesswork - but very good guesses. The most well-known and successful technology that has resulted from this process is the MJOLNIR energy shield generators, which have formed the basis for all post-Reach shield technology - but they are certainly not the only success story the Navy has seen.

Developed concurrently, the Thanatos-Class Prowler made use of reverse-engineered prototype active camouflage, appropriated from the combat harnesses of stealth and special operations Elite warriors and crashed stealth corvettes. Initially limited in its capabilities and efficiency, numerous updates would dramatically improve the class's effectiveness, and the technological exchange that followed the conclusion of the war would usher in a new age for the class, where their usefulness would be paramount. Only seventeen were ever built, and though the Navy refuses to confirm or deny that any have been destroyed, records seem to indicate that only three have ever been lost to enemy fire. Most details about them are classified November Black, other than the occasionally unreliable material the Office of Naval Intelligence includes in its propaganda.


For the most part, the ONI Prowler Corps has had little interest in developing Covenant active camouflage systems - while their systems would indeed render a starship optically invisible, as well as concealing their thermal and radiation signatures, there are considerable and potentially life-threatening problems that must be circumvented. Optically optical invisibility would also neccessarily render the starship blind, forced to rely on pre-calculated trajectories for stellar debris, and unable to account for enemy warship movements, effectively unable to detect potential hazards - more importantly to the Prowler Corps, it would also mean that a Prowler would effectively become useless at its primary role, as a stealth reconnaissance and electronic warfare platform. Until a means could be found to circumvent this limitation like the Covenant could, ONI primarily ignored such a system in favour of the traditional combination of stealth ablative coating, photoreactive panels, and internal heatsinks to avoid detection for a limited time.

When Project TEMERITY therefore made its breakthrough in Active Camouflage technology in 2545, the Prowler Corps was understandably unenthusiastic at the prospect of replacing its entire fleet with the new system. Believing that their hesitation was a result of a lack of confidence in the results of the technology, TEMERITY personnel began the conversion of the Mako-class corvette UNSC Nanuchka to incorporate the technology. Designated the IX-866, codenamed "Orcus", initial demonstrations showed more promise than the representatives from the Prowler Corps had hoped for, allowing total impenetrable stealth, although problems arose with the heatsinks due to power requirements - though seeing considerable potential for the technology, the Prowler Corps chose to wait until it had been developed further. The development facilities at Byblos Testing Station would be destroyed as the Covenant continued its relentless conquest of the Outer Colonies, but the prototype would survive in the orbital shipyards above Reach, withdrawn for further analysis and testing.

As technological developments continued to be made, the efficiency of what would later be known as the Orcus-class active camouflage system would greatly benefit. A heightened understanding of the concept would be derived from captured combat harnesses acquired from dead Elite stealth and special operations warriors, and reverse-engineered to limited success; Intended fleetwide upgrades to fusion reactor design would triple the longevity of the ships ability to remain "cloaked"; and internal changes at ONI would see a surge of support for the concept, replacing the scepticism of the previous administration. The prototype recieved an extensive upgrade, being redesignated "Orcus II," and would participate in an insertion and extraction mission, launching a team of SPARTAN-II supersoldiers to board a Covenant ship and recover a valuable "package". The success of the ships deployment and continued evasion of Covenant sensors would be the success Project TEMERITY had been hoping for - with the backing of the Director of ONI, Margaret Parangosky, Project ORCUS recieved an extensive increase in funding, and the class was put into production as the Thanatos-Class Prowler.

The first production models would enter service shortly before the Battle of Delta Pavonis - given the extremely classified nature of the technology employed, and their mission role, their early history is unable to be determined in concrete terms. There is some indication that at least two were present at the Battle of Delta Pavonis, while another two (or perhaps the same two) were present at Minorca during Operation: HOT GATES. Afterward, their mission history becomes even more difficult to determine, given the chaotic nature of the next few months - the invasion of Reach, and the subsequent battle at Earth. Given the fleetwide recall instituted after Reach, it is likely that all then-current models were present for the battle, providing crucial attack staging areas for boarding parties, covert nuclear missile launch, mine placement, and other vital roles.

With the development of Tarnhelm Metamaterial, ONI would abandon the use of active camouflage technology, deeming it too cost-inefficient for the future fleet, placing their faith in the new metamaterial. The Thanatos-class would continue to serve in the Navy during the War of Vengeance, but would remain the last examples of pre-war technology as new ship classes entered service, replacing the old. After 2566,


There are a number of limitations inherent in the design of the Thanatos-class Prowler's active camouflage system

Ships of The Line