"To push back the night. To rule the stars themselves."

— Unofficial fleet motto, Battlefleet Koronus
Battlefleet Koronus

Battlefleet Koronus vessel departs Port Wander to undertake another Long Patrol

Battlefleet Koronus, officially known as Passage Watch 27-Est, is a small fleet of Imperial Navy vessels charged with the protection of the Koronus Expanse, a dangerous unexplored region of the Halo Stars located beyond the Calixis Sector in the Segmentum Obscurus, which lies on the northern edge of the known galaxy.

At the docks of Port Wander, through the Koronus Passage, and into the Expanse beyond, the grey-hulled and crimson-prowed ships of Battlefleet Koronus defend Imperial interests and provide a bulwark for the Calixis Sector against the horrors that lurk in the depths of the Halo Stars.

Officially known as Passage Watch 27-Est, this fleet detachment is nominally under Calixis Sector Command, but given a great deal of leeway in pursuing its directives -- defend Port Wander and other Imperial outposts and void stations along the Halo Margins, patrol the Koronus Passage, and launch expeditions into the Koronus Expanse to eliminate potential threats to the Calixis Sector.

These actions gave rise to the detachment's unofficial name amongst Navy personnel and civilians alike -- Battlefleet Koronus. This squadron, commanded by Fleet-Captain Nathaniel Horne, is on extended detached duty from the rest of Battlefleet Calixis.


Passage Watch 27-Est

Koronus Expanse of the Halo Stars

Departmento Graphicae Map of the Koronus Expanse

From the first discovery of the Koronus Fragments amongst Segmentum Obscuras naval records in 101.M38, the Imperium knew there might be unknown threats beyond the raging Warp Storms at the edge of the Calyx Expanse. These purported records of an unknown Explorator fleet told of mineral-rich worlds, habitable biospheres, and alien empires in the Halo Stars rimward of the Calyx Expanse.

As the Angevin Crusade forged those lawless regions into the Calixis Sector, the Imperial Navy probed the edges of the Drusus Marches Sub-sector, searching for passages through the vast storms. None could be found, and the Navy ceased searching in the years after the Crusade, as warships returned to their former battlefleets and the sadly depleted remnants formed the nucleus of the nascent Battlefleet Calixis.

Several centuries later, Sector Command founded Port Wander, a heavily-armed voidstation to serve as a staging ground for Navy operations along the Halo Margins. Navy presence soon dwindled as unrest drew the Battlefleet Calixis' attentions elsewhere, and the station came under the control of miscreants and Rogue Traders.

Even so, when the Rogue Trader Purity Lathimon finally discovered the nigh-mythical Koronus Passage through the Great Warp Storms into the Expanse, Battlefleet Calixis set a watch on this gateway to the Halo Stars. The first Passage Watch Est was led by Terrich Voyle, who commanded the force from the Gryphon, his grandfather’s old flagship.

Affairs continued in this manner until the Ork WAAAGH! Gulgrog smashed through the Maw and laid siege to Port Wander. Though the story of Port Wander's siege is best told elsewhere, suffice it to say that most Rogue Traders fled or avoided the conflict. The siege broke two years later, when Passage Watch 27-Est rendezvoused with reinforcements from Port Wrath and a fleet sent by the Adeptus Mechanicus from the Lathes. The combined forces defeated the Orks, liberating the imperilled station. WAAAGH! Gulgrog had two lasting effects on Imperial policy.

The first was to lend ammunition to arguments that Port Wander should be returned to Imperial Navy control. For decades prior to the Ork attack, prominent individuals in the Imperial Adeptus and Calixis Sector nobility had been petitioning the Lucid Palace on the sector capital world of Scintilla to end the so-called "rule" of Rogue Traders and merchant guilds on this important way point to the newly discovered Koronus Expanse.

Port Wander's near demise (and the haste with which many of its most powerful residents abandoned it in its time of need) was the tipping point in these debates. Within several decades, the voidstation was returned to Navy command.

The second effect was less-noted but would prove equally important. Acting on its own recognizance, Battlefleet Calixis's upper echelons decided an intermittent patrol was insufficient to defend against incursion through the Koronus Passage. In recognition for its heroism during WAAAGH! Gulgrog, Passage Watch 27-Est was re-tasked as a permanent detachment, operating semi-independently from Battlefleet Calixis. For more than 350 standard years, Passage Watch 27-Est kept this vigil.

Battlefleet Koronus

Established in 673.M40, Battlefleet Koronus is not large, especially compared to Battlefleet Calixis as a whole. It is comprised of several Cruisers, Light Cruisers, and Battlecruisers, supported by multiple Destroyer and Frigate Escorts. These warships possess most of the combat experience in Battlefleet Calixis, as they are almost constantly in conflict with raiders, pirates, and the occasional xenos vessel that comes through the Maw to plunder the Calixis Sector. Passage Watch 27-Est is hard-pressed but vigilant, and on occasion has sent its distinctive grey-hulled, crimson-prowed vessels on counter-actions and reprisals into the Koronus Expanse.

Today, Battlefleet Koronus operates largely independently of the sector's overview. It is one of the few fleet detachments not to lose forces to the ongoing demands of the "Margin Crusade," and has even seen a slight growth in strength as exploration and interest in the Koronus Expanse grows.

Defending the sector against the predications of the Expanse is one duty that cannot be allowed to lapse, and since one of Battlefleet Koronus' tasks is to protect Zone 15 (and the Warp Gate to the Jericho Reach), its ships are so far immune to requisition.

Battlefleet Koronus stages from several locations, including Port Wander in the Rubycon II System, Copernicus Depot at the edge of the Drusus Marches, and Fleet Base Metis in Zone 15. However, with the exception of Fleet Base Metis, few warships may be found at these locations at any one time. The majority of Battlefleet Koronus is on constant patrol, the better to project its power.

Long Patrols

"You've made quite a few mistakes in this engagement, Captain. However, your first was assuming that the Emperor’s wrath would be stayed by a mere boundary."

— Admiral Nathaniel Horne, during the pursuit and subsequent capture of the raider Vicious
Battlefleet Koronus' most powerful vessels rarely range beyond the Maw, leaving patrol work to the Frigates of Triumph Squadron and Light Cruisers such as Aegis, Hawk, and Swiftsure. These vessels travel deep into the Expanse, often remaining on patrol for years, even solar decades, at a time.

These "Long Patrols" avoid conflict if possible, and do not actively hunt down pirates, xenos, or other malcontents. Rather they scout the reaches of the Expanse, investigating uncharted worlds, keeping an eye on the activities of Rogue Traders, and monitoring the status of known threats and xenos empires.

These patrols require a ship and crew that are self-reliant and versatile, and a captain both quick witted and able to operate independently from the chain of command without becoming either ineffectual or a Renegade. In fact, those captains who have proven particularly adept at the Long Patrol tend to seem more Rogue Trader than Navy officer.

Most Rogue Traders avoid direct conflict with Navy vessels in the Expanse. However, once beyond the Maw or Metis Base, the laws of the Imperium mean nothing, and the only authority a Navy vessel has is that which is wrought by cold steel and Macrobatteries. Some Rogue Traders do not take kindly on what they see as the prying eyes of the Imperium investigating their business, and may show their displeasure with action.

However, a Navy ship has far worse threats to contend with in the form of Chaos Reavers, pirate wolfpacks, Ork Freebooters, Eldar Corsair, and the dreaded Rak'Gol, not to mention the dangers of Warp Storms, grav-tides, supernovas, or a host of other "natural" threats. The Long Patrol is a coveted responsibility for the chance to win glory and honour, but it is a highly dangerous task just the same.

Patrols of Note

Battlefleet Koronus regards certain Long Patrols as particularly important, assigning them trusted captains and reliable vessels.

  • The Vigil of Undred-Undred Teef - The Ork worlds of Undred-Undred Teef are an obvious source of danger for the Imperial interests in the Koronus Expanse, as well as the entire Calixis Sector. However, ever since the loss of the Light Cruiser Rhadamanthine during a reconnaissance of the region, the Navy has chosen discretion for their patrols. Currently, the Sword-class Frigate Lord Marius Hax lurks in the outer Oort Cloud of the Stompgit System, hidden amongst a clutch of rocks and ice. Retrofitted for an extremely extended deployment, the Frigate may remain there for several decades, though Commander Larren Volos occasionally patrols nearby star systems to see how far the Ork infestation spreads.
  • Investigating the Alenic Depths - As the Rak'Gol threat grows, Battlefleet Koronus has dispatched the Falchion-class Frigate Swift Judgement to the edges of the Alenic Depths in hopes to gather more information about these mysterious xenos. Commander Halik Kail is under orders to exercise extreme caution, but the vast distance and stellar disturbances means communications with the ship have been sporadic at best.
  • Piracy in Winterscale's Realm - One of the few "explored" regions of the Expanse, the worlds in Winterscale's Realm are mostly likely to have regular contact and trade with the Imperium. As the value of this trade grows, Horne dispatched Captain Sasha Rivers and the Dauntless-class Light Cruiser Swiftsure to protect Imperial interests in the region. Thus far, the captain has destroyed three pirate vessels and taken two additional raiders as prizes -- success enough that the scattered pirate clans of the region are banding together in an attempt to destroy her.
  • Struggles in the Foundling Worlds - Endeavours in the Foundling Worlds have suffered of late, from plagues, Warp Storms, and raids by pirates and xenos. The Sword-class Frigate Scintilla Majoris, Commander Helgrom McKrale commanding, has been patrolling the Foundling Worlds for the past five years, and has found itself caught in the midst of conflict. Of particular threat are the Chaos Reavers of Iniquity, and the Scintilla Majoris engaged them in several desperate battles within the last few years. Now, running low on supplies and ammunition, McKrale searches for a safe port where he can repair, re-provision, and reinforce his depleted crew.

Zone 15


A starship begins passage through the Jericho-Maw Warp Gate

Originally the Fifth Station of Passage through the Maw, within the last century Passage Watch 27-Est has blockaded this small, barren star system (itself outside the more explored portions of the Koronus Passage) and a vast portion of surrounding space and declared it off-limits to any unauthorised vessels. Few Rogue Traders (or any non-Navy personnel, really) know what secrets lie within its borders.

In truth, Zone 15 was established on discovery of a marvellous relic, an ancient xenos Warp Gate that allows ships to travel across the galaxy to the far-flung Jericho Reach in the Eastern Fringe. Originally, Passage Watch 27-Est merely watched over the gate as Adepts from the Adeptus Mechanicus investigated its mechanism and, more importantly, where it led.

Later, as the powers of the Adeptus Terra decided to launch a Crusade through the gate to reclaim the Reach, Battlefleet Koronus switched to the role of guardians. Not only did they guard this vital supply line for the Achilus Crusade, they also protected the secret of the Warp Gate's existence.

In hindsight, it was inevitable that Battlefleet Koronus would establish a permanent base in the region. Though the gate is actually located in the black depths of space, the Navy established their base in a nearby star system: System Designate 028-3B8-4D. This served their purposes two-fold, not only did the system provide many of the necessary resources to establish an installation, but it also added another layer of misdirection. Anyone looking for a Warp Gate would focus their attentions on a known Navy fortress, and not think to explore the void several thousand astronomical units distant.

Fleet Base Metis

Ramilies-class Starfort

Fleet Base Metis, a Ramilies-class Starfort

System Designate 028-3B8-4D is a barren collection of rocks orbiting a guttering red dwarf. Besides several rings of asteroids (the innermost being semi-molten), the only worlds in the system are several marginal telluric rocks with thin, dusty atmospheres of inert gas. In fact, its only appealing feature besides the Warp Gate is that it is near the centre of a relatively large region of space where Warp Storms do not intrude.

Fleet Base Metis does not orbit any of these worlds, instead following an orbit amongst the outmost asteroid ring. Imperial strategists cunningly calculated the placement of the voidstation so the approaches are limited by the surrounding field, and several seemingly accessible approaches are covered by minefields and Macrobattery emplacements built into the larger rocks. The shifting orbital paths of the asteroids, coupled with the formidable perimeter defences and Battlefleet Koronus warships on station, make simply approaching the Fleet Base an onerous task.

Even if a foe could reach Metis, they may well find themselves outclassed by the firepower the voidstation can bring to bear. The base itself is an extremely powerful bastion, a Ramilies-class Starfort. Originally designed by Artisan Magos Lian Ramilies from STC components, the Ramilies is as heavily armed as a squadron of warships and can remain self-sufficient for decades if not indefinitely. More importantly, a Ramilies can erect a Warpbubble over the entire structure, enabling it to enter the Warp and be towed by fleets of tugs to different star systems.

Originally commissioned for the Achilus Crusade into the Jericho Reach, Fleet Base Metis was towed to System 028-3B8-4D in preparation for transport through the Warp Gate. However, last-minute studies of the gate and its properties by the senior Magi of the Adeptus Mechanicus determined it would not survive the journey. Transit through the gate is extremely turbulent, too much so for an unwieldy convoy of tugs and supply ships towing an unwieldy Starfort.

Unfortunately, just passing through the Maw had proven extremely dangerous for the procession, and the risk of taking Metis back into the Calixis Sector was deemed too great. After the strategists who suggested using Metis in the Crusade had been punished for incompetence, the massive starfort was left in System Designate 028-3B8-4D, where it was reassigned to Passage Watch 27-Est almost by default.

Since its accidental arrival, Metis has proved incredibly useful to the Achilus Crusade and Battlefleet Koronus. Not only is it a vital resupply and staging point for Fleet-Captain Nathaniel Horne's fleet, it also serves as a transit point for a large portion of the supplies still flowing through the Warp Gate to the Jericho Reach. Although some void ships travel directly to the gate, many others off-load their cargos at Metis and depart, never knowing the ultimate destination of their supplies. In turn, other ships make a continuous run through the Warp Gate to the Imperial Fortress Worlds on the far side.

Notable Vessels of Battlefleet Koronus

  • Gryphon (Mars-class Battlecruiser) This venerable Mars-class Battlecruiser has served with Battlefleet Koronus since its inception, often as the detachment's flagship. Many foes have fallen to its powerful and fearsomely accurate Nova Cannon, until the ship is known, and feared by the Imperium's enemies, throughout the regions of the Expanse near the Maw. Almost as renowned are the Gryphon's Attack Craft squadrons, especially the Fury interceptors of Tempest Wing and the Starhawk bombers of Absolution Wing. Currently, the Gryphon is under the personal command of Fleet-Captain Horne, and consequently patrols between the detachment's staging points.
  • Stormwind (Overlord-class Battlecruiser) - This powerful Overlord-class Battlecruiser is better suited for full warfare than long-range patrols, and some wonder how it ended up assigned to the Passage Watch at all. In truth, Battlefleet Calixis was loath to lose this vessel to the demands of the "Margin Crusade" and the ongoing war in the Jericho Reach, and transferred it to the Passage Watch instead. The Crusade's masters could hardly protest without raising unwanted attention amongst those who do not know the true nature of the Margin Crusade, which is simply an excuse to hide the existence of the Achilus Crusade and the Calixis Sector's role in supporting an Imperial Crusade on the other side of the galaxy. Now, the Stormwind spends much of its time commanding the blockade forces around Zone 15, but provides a powerful reserve should the Passage Watch or Battlefleet Calixis find itself in a full-blown war.
  • Sirius (Lunar-class Cruiser) - A stalwart Lunar-class Cruiser with an impressive record of service, the Sirius fought with distinction in the Battle of Gethsemane during the Gothic War of 143-151.M41, helping to throw back Abaddon's attempted conquest of the Gothic Sector. It was subsequently transferred to Battlefleet Calixis, then to Passage Watch 27-Est. The Siriuss veterans constantly train new recruits, so that the warship's crew has earned a reputation as being particularly competent. The Sirius often patrols the Maw entrance in the company of the Gethsemane.
  • Gethsemane (Gothic-class Cruiser) - Something of a rarity in a Battlefleet, this Gothic-class Cruiser is newly constructed, built within the last century at the Drystan Construction Yards. Its crew is still considered "green," hence its pairing with the veteran Sirius. It is rumoured that Fleet Command finds it amusing to partner the ship with a vessel that fought in the battle the Gethsemane is named for.
  • Hand of Redemption (Lunar-class Cruiser) - Under the command of Captain Keel, this Lunar-class Cruiser spent several years on "extended patrol" in Winterscale's Realm. Upon his return, his familiarity with the Koronus Expanse meant Battlefleet Command felt it was worth transferring him to the Passage Watch.
  • Drake (Tyrant-class Cruiser) - A Tyrant-class Cruiser, the Drake recently returned to service after being trapped in the Immaterium for five years by the violent Warp Storms bordering the Maw. That the warship survived either makes it lucky or suspect, depending on whom one asks.
  • Warspite (Dictator-class Cruiser) - Like most Dictator-class Cruisers, the Warspite began life as a Lunar, and was converted into an Attack Carrier vessel to better serve the needs of Battlefleet Koronus. Its duties alternate between convey patrols around Port Wander, and showing the flag at outposts beyond the Maw.
  • Swiftsure (Dauntless-class Light Cruiser) - Battlefleet Koronus finds Light Cruisers exceedingly useful in anti-piracy patrols, and the Swiftsure is one of several Dauntless-class vessels in the Passage Watch's ranks. Under a succession of aggressive (and slightly brutal) captains, it has become the bane of Cold Trade smugglers who run the Maw.
  • Hawk (Defiance-class Light Cruiser) - Voss Pattern vessels are rare this far from the world of Armageddon, and this Defiance-class Light Cruiser/Attack Carrier is the only one of its kind in Battlefleet Calixis. Light Cruisers outfitted as Attack Carrier vessels are thought of as an unworkable hybrid vessel by many Navy officers, and Hawk was transferred to the Passage Watch mostly because Sector Command was unsure what to do with her. Under the command of Commander Victoria Horne, however, Hawk consistently patrols deep into the Expanse, and has proven a valuable source of intelligence to the Battlefleet.

Notable Squadrons of Battlefleet Koronus

  • Triumph and Wrath of Saint Drusus Squadrons - Squadrons of Sword-class Frigates and Cobra-class Destroyers, respectively, are both cornerstones of Battlefleet Koronus' attempts to interdict smuggling and piracy. The Destroyers in Wrath of Saint Drusus Squadron are noted for destroying the wolfpack reaver warship Blooded Skull in a three-day running battle.


  • Rogue Trader: Battlefleet Koronus (RPG), pp. 58-59, 63-64
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