View source for Battle of Bastior

{{Battle3
|Name         ={{PAGENAME}}
|Image        =Grendyllus.jpg
|Image caption=[[Imperial Guard]] battle [[Tyranids]]
|Conflict     =[[Fourth Tyrannic War]]
|Date         =[[M42]]
|Location     =[[Bastior Sub-sector]]
|Outcome      =Imperial tactical victory. Bastior holds but many of its worlds are lost and the Tyranids continue to plague the region
|Combatant1   =[[File:Aquila1transparent.png|30px]] [[Imperium]]
|Combatant2   =[[File:Tyranid logo.png|30px]] [[Tyranid]]s
|Combatant3   =Misc. [[Xenos]]<br><br>[[File:Orks.png|20px]] [[Orks]]<br>[[File:Eldar.png|20px]] [[Craftworld Eldar]]<br>[[File:DarkEldar.png|20px]] [[Dark Eldar]]<br>[[File:LOVSymbolTransparent.png|20px]] [[Leagues of Votann]]<br>[[File:Ankh triarch.png|20px]] [[Necrons]]<br>[[Hrud]]<br>[[Mebrii]]<br>[[Ghluthykk]]
|Commanders1  =[[File:Astra Militarum Symbol.png|20px]] [[Lord Commander Solar]] [[Arcadian Leontus]]<br>[[File:CustodesSymbolClear.png|20px]] [[Captain-General]] [[Trajann Valoris]]<br>[[File:Aquila1transparent.png|20px]] [[Groupmaster]] [[Tysen Yacobe]]<br>[[File:IFsymbol.png|20px]] [[Space Marine Captain|Captain]] [[Tor Garadon]]<br>[[File:Ultramarinessymbol.png|20px]] [[Space Marine Captain|Captain]] [[Severus Agemman]]<br>[[File:White Templars symbol.jpg|20px]] [[Chapter Master]] [[Kruxor Stavro]]
|Commanders2  =[[File:Tyranid logo.png|20px]] [[Hive Mind]]<br>[[File:Tyranid logo.png|20px]] [[Swarmlord]] (MIA)
|Commanders3  =[[File:Orks.png|20px]] [[Warboss|Monsta-Boss]] of Glowing Rokk
|Strength1    =See Order of Battle
|Strength2    =[[File:Tyranid logo.png|20px]] [[Grendyllus]], consisting of many billions of Tyranids
|Strength3    =[[File:Orks.png|20px]] [[Waaagh!]]<br>[[File:ThurianSymbol.jpg|20px]] [[Greater Thurian League]]<br>[[File:KronosSymbol.jpg|20px]] [[Kronus Hegemony]]
|Casualties1  =Heavy
|Casualties2  =Massive
|Casualties3  =Heavy
}}
The '''{{PAGENAME}}''' is a major campaign of the [[Fourth Tyrannic War]].{{Fn|1}}

===Overview===
====Grendyllus Rising====
After the appearance of a major [[Fourth Tyrannic War|new offensive]] by [[Hive Fleet Leviathan]], the twin [[Imperial]] strategies of [[Solblades]] and [[Anchor World]]s seemed to stabilize the situation against the twin Tyranid tendrils of [[Nautilon]] and [[Promethor]]. However all this changed when a third tendril dubbed [[Grendyllus]] sprang up from below the galactic plane undetected and rapidly consumed swathes of both Imperial and [[Xenos]] territory right under the noses of [[Terra]].{{Fn|1a}}

It was [[Battle Group Faustus (Fleet Sextus)|Battle Group Faustus]] of [[Indomitus Crusade Fleet Sextus]] under [[Tysen Yacobe]] that first raised the alarm that something was amiss after four of his own task forces went missing. Soon enough, survivors emerged at the fringe of the [[Circeyl System]] bringing word of alien horrors, and the message quickly reached Groupmaster Yacobe. Yacobe along with much of Faustus was anchored at the world of [[Sanctum]] within the [[Formidyre System]], a lynchpin of the defense of the [[Bastior Sub-sector]] which lay within Grendyllus' path. Even more significant, the massive ''[[Phalanx]]'' itself with [[Lord Commander Solar]] [[Arcadian Leontus]] was also anchored at Sanctum, coordinating the war effort against the Tyranids.{{Fn|1a}}

Already, the forces of Grendyll were overrunning much of the outlying Sub-sector and the [[Shadow in the Warp]] began to descend across the region, driving many [[Astropath]]s insane. Seeing the security of Sanctum and Lord Leontus was now at risk, Yacobe volunteered to take his remaining forces and move deep into the Sub-Sector to buy time by stemming the alien advance. Meanwhile, panic, confusion, and even denial erupted across [[Lethnor]], [[Gainder's Hope]], [[Unspake]], and the [[Gallospire System]]. However at [[Welm]], [[Tzeng-Raan]], and [[Aggrandia]] the response was more stable, with [[Regiment]]s of [[Imperial Guard]] being mobilized to meet the threat. Despite this, all in Leontus' command staff knew that it would not be enough to stop this new Hive Tendril. Whether by predatory instinct or by a higher design, Grendyllus had spearheaded deep in the Imperial rear and was bypassing most of the [[Solblade]]s and even much of the [[Sanctus Line]].{{Fn|1a}}

Leontus responded by enacting the '''Sanctuary Protocol''', sending desperate requests for reinforcements from [[Segmentum Solar]] and [[Solblades]]. In the meantime, Imperial forces remaining in Bastior were ordered to fall back to the [[Formidyre System|Formidyre]], [[Pyremoat System|Pyremoat]], and [[Kastayl System|Kastayl System]]s. These were to salvage all ammunition, fuel, and manpower they could and avoid engaging the Tyranids in protracted battles. Those that could not withdraw were ordered to dig-in and do the best they can.{{Fn|1}}

====Tyranid Advance====
While the [[Promethor]] and [[Nautilon]] tendrils were spread over multiple sectors, those of Grendyllus were all concentrated in a single sub-sector of space. Why was unclear, but some theorized it may be a form of concentrated counterattack.  Meanwhile, the strength of the three primary sanctuary systems of Bastior grew thanks to a constant stream of arriving reinforcements from elsewhere. Those who could not flee simply resigned themselves to their fates, while on [[Lethnor]] the nobility engaged in mass debauchery which resulted in a mass rebellion even as the Tyranids consumed their world. In the Irontower System, Captain [[Veshwalde]] of the [[Kordessan Light Infantry]] was able to lead a spirited defense on the world of [[Donjorr]] despite their inevitable doom. In the Reydabt System, initial Tyranid attacks against the [[Agri-World]] of [[Cornucog]] were defeated, but during the infamous Nine Days of Blood the xenos managed to overrun the defenses of the Mariavahl Line. Rather than lose heart, the Imperial forces trapped on the doomed world fought to the last and shockingly were able to fight the Tyranids to a stalemate.{{Fn|1b}}

The Imperium was not alone in resisting the Tyranids. [[Ork]] hordes under [[Orzgog]] attacked the Tyranids in the [[Kheepgen System]] and [[Formidyre System]], delighted to find a good fight on their doorstop. Elsewhere, forces from the [[Greater Thurian League]] and [[Kronus Hegemony]] rallied the [[Leagues of Votann]] scattered throughout the asteroid belt dubbed [[Saint Catherine's Tears]]. Abandoned by their own leaders, many [[Human]]s joined the [[Squat]]s in an alliance. In the [[Palat System]] the Tyranids, [[Necrons]], [[Craftworld Eldar]], and [[Dark Eldar]] engaged in a vicious four-way-war that saw unimaginable superweapons unleashed by all sides. Tyranids were able to spill into the [[Webway]], triggering a separate and equally vicious conflict outside the bounds of reality. In addition to this, [[Hrud]], [[Mebrii]], [[Ghluthykk]] viro-combines, and even [[Jokaero]] star-frames engaged the Tyranids in their own battles.{{Fn|1b}}

Despite a heroic resistance, the Imperials were being worn down through attrition while the Tyranid numbers seemed limitless as they launched wave after wave of massive attacks that sometimes were only hours apart. In the [[Stanghalde System]], Tyranids managed to overwhelm the orbiting [[Imperial Navy]] defenders in the 11th attack on [[Portent]]. Before being consumed, Imperial defenders reported that a [[Swarmlord|four-armed Hive Tyrant of unprecedented ferocity]] was leading the attack. The Reydabt System nearly fell shortly after, with the worlds of [[Welm]], [[Maur]], [[Dvze]], and [[Rov]] succumbing to the 19th Tyranid attack. However, the Xenos were still unable to fully overrun the major settled planets of the System. In the [[Gallospire System]], the War of Closed Eyes had seen countless Imperial lives in civil strife. [[Priest|High Frater Niyellus]] was still in denial about the existence of Xenos, even as the Tyranid fleet appeared above the world. The remaining loyalist defenders suffered terribly in the ensuing mayhem.{{Fn|1b}}

As resistance lessened in the wider sub-sector, the Tyranids massed and surged up to attack the [[Pyremoat System]]. [[Bio-Ship]]s bypassed the radiation storm belts around the System to assail its worlds just as mutated Orks led by the Monsta-Boss of Glowing [[Rokk]] arrived. Faced with two alien foes, deep-void stations were quickly overrun along with the industrial moon of [[Eleidee]]. Soon after, [[Admiral]] [[Ranjav]] was forced to fight both Tyranids and mutated Orks in the chaotic Battle of Gaithaus Sound. Ranjav was able to hold her own for a time, but ended up losing half-a-dozen vessels alongside her flagship, the [[Oberon Class Battleship]] ''[[Spirit Aflame]]''. Planetary invasions followed thereafter, with the [[Hive World]] of [[Trygg (World)|Trygg]] facing mechanised Ork hordes while the Scriptorum World of [[Blohtt]] was assaulted by Tyranids and Greenskins at the same time. The only saving grace for the Imperial defenders was that the Tyranids and Orks slaughtered each other as willingly as they did humanity. This allowed the Imperials to redouble their defences at the [[Kastayl System]], where [[Space Marine]]s, Imperial Navy, and [[Adeptus Mechanicus]] warships were able to prevent a single Tyranid or Ork from making planetfall.{{Fn|1b}}

Ultimately, the Tyranids broke the Imperial orbital defences at Kastayl by using massive psychic Bio-Ships known as [[Mindslayers]] to spread terror and hallucinations in the Imperial crews. Tyranid swarms followed in the Mindslayers wake, allowing the Tyranids to gain a foothold on the [[Battery World]] of [[Rakhnor]] and the [[Agri-World]] of [[Rashlav]].{{Fn|1b}}

====Sanctum====
[[Image:SanctumWar.jpg|thumb|right|220px|The war for the Formidyre System{{Fn|1c}}]]
With most of the key Imperial systems of the Sub-sector burning, it seemed inevitable that the Formidyre System would soon under be attack as well. When the attack did finally begin, it was relentless and saw unending swarms of Bio-ships swarm  up through the ecliptic plane and encircle the system. Hour by hour, the Tyranids arrived in massive numbers and the Shadow in the Warp thickened to spread terror and despair amongst the defenders. So densely packed were the Tyranids that they became visible on the surface of planets within the system during daylight. It was at this moment that Leontus' careful planning played off, and [[Ministorum]] propaganda broadcasts were broadcast across the System to inspire the defenders and drown out the terror caused by the Shadow in the Warp. Surprisingly, the strategy worked and the Imperial defenders held their positions in anticipation of the enemy.{{Fn|1c}}

Ferocious battles erupted around the [[Industrial World]] of [[Phraktam]], the laboratory world of [[Lembyq]], and the [[Hive World]] of [[Oghram]] as Imperial Navy flotillas and planet-based orbital defenses opened up on the xenos. On the mortuary world of [[Krematos]], Tyranid vanguard organisms like [[Genestealer]]s and [[Lictor]]s engaged in subterranean warfare with the Imperials. On the [[Feudal World]] of [[Jovenghast]], a [[Genestealer Cult]] erupted from amongst the serf population led by tainted nobles of [[House Veilchayn]]. The uprising spread anarchy throughout the worlds northern hemisphere as loyalist cavalry and archers met alien horrors and cultists armed with contrabrand firearms. Yet the tide turned when the loyalist [[Knight]]s of [[House Terryn]] and [[House Griffith]] arrived. All the while, the Tyranids continued to advance throughout Formidyre despite the ferocious Imperial resistance. Leontus next dispatched Imperial Navy, Space Marine, and Mechanicum fleets forward to try and blunt the Xenos advance. All took their toll, but none could stop the swarm due to its sheer numbers.{{Fn|1c}}

While the Kastayl System held thanks to the [[Deathwatch]], [[Sisters of Battle]], and [[House Taranis]] and the Pyremoat System was the site of massive battles between the [[Legio Abjuror]] and Tyranid [[Bio-Titan]]s on the night world of [[Vohyd]], the Tyranids were soon at the doorstep of [[Sanctum]] itself. As the Xenos arrived, Leontus made his command headquarters within the [[White Templars]] [[Fortress-Monastery]] of [[Holdfast]]. At the same time, Imperial defenders dug-in at the series of asteroid-based defensive bastions dubbed the Dornwall. Despite its formidable defenses and the accompanying flotillas of Imperial Navy ships, one by one each asteroid fortress was broken up and captured by the Tyranids. In particular, [[Toxicrene]]s and [[Venomthrope]]s proved capable at suffocating the defenders out. As resistance in the Dornwall began to falter, heavier [[Hive Ship]]s ploughed through the asteroids and created openings which allowed smaller swarms to follow.{{Fn|1c}}

The incoming Tyranid fleet not came face-to-face with the enormous Imperial fleet commanded by Groupmaster Yacobe in orbit over Sanctum. It was then that even more Tyranid bio-ships arrived, surging through gaps in the Dornwall to encircle the planet and attack from every direction. However the massive ''[[Phalanx]]'' itself stood in the way, opening up on the Tyranid fleets and reaping massive tallies. 300 [[Imperial Fists]] under [[Tor Garadon]] stood aboard the station, vowing to give their lives to defend their ancestral fortress. The prime directive of the Imperial vessels was to prevent any Tyranid bio-ships from slipping through onto Sanctum while the secondary objective was to eliminate large [[Hive Ship]]s. In the end, the Imperials were more successful in the secondary objective than the first and due to their sheer numbers numerous Bio-Ships were able to slip through the defending armada and make for Sanctum's surface. Despite ferocious ground-to-air battery fire, the Tyranids were able to land billions of warrior organisms on Sanctum's surface.{{Fn|1c}}

Again and again, the Tyranid ground invasion was met by determined armoured counter-attacks and artillery saturation. At the Kzarvin Steppes, a dozen Imperial Guard [[Regiment]]s fought tirelressly to keep three Tyranid swarms from melding together into a single super-swarm that could threaten Cruxharbour from the south. As their fight became even more desperate, [[Titan]]s of the [[Legio Destructor]] marched out in support to engage colossal [[Hierodule]]s and [[Tyrannofex]]es. In the forests of Voth's Reach, [[Sisters of Battle]] of several orders fought side by side and incinerated swathes of xenos before being forced to pull back to their fortresses. But just as in space, sheer numbers took their toll and the Tyranids were able to slowly create openings in the Imperial lines to exploit. The assault of individual swarms began to interlock and offer mutual support, allowing some Tyranid waves to expend themselves to allow others to outflank the Imperials. At the Pentacastes Plains, the [[Swarmlord]] itself appeared to threaten Holdfast itself.{{Fn|1c}}

By now, the Imperials were in a forced retreat to their primary fortresses to dig in. Some of these holdfasts held firm, while others were overrun by sheer numbers. Orbiting Imperial ships were sometimes forced to bombard their own positions in order to prevent a full xenos breakthrough. At Four Luthiorn, a mass of psychic Tyranid organisms drove the defenders into a state of mindless terror that saw many of them butcher one another before the Tyranids had even arrived. The entire Olvenbach Line fell in a day after a single soldier was infected by a [[Parasite of Mortrex]]. But amidst all this slaughter, none was assailed worse than Holdfast. A massive Tyranid swarm initially mistaken for a collapsing tectonic fault emerged from the Heights of Artorus to attack the White Templars fortress with hundreds of [[Trygon]]s and [[Mawloc]]s at its spearhead. In their rear lurked new [[Norn Emissary|Norn Emissaries]], who fixed their sight on Leontus and his command staff.{{Fn|1c}}
[[Image:ValorisvsNorn.jpg|thumb|right|250px|[[Trajann Valoris]] leads [[Custodes]] against a [[Norn Emissary]]{{Fn|1c}}]]
Two colossal Tyranid super-swarms closed upon the Heights of Artorus like the jaws of a beast. Leontus and his staff were undeterred however, and they skillfully oversaw a defense to hold the xenos back as [[Chapter Master]] [[Kruxor Stavro]] fought on the frontlines. However the Tyranids came without pause day by day, and gradually the Imperials gave more ground. On the eighth day of the siege, a Norn Emissary emerged inside the fortress to massacre the command staff of the Erythrad Peak sanctum. The beast would have escaped had a nameless [[Chapter Serf]] not given their own life to seal the creature inside the sanctum with it before detonating plasma charges. The second Emissary, known as the '''Fiend of Hag Rift''', emerged with lesser organisms and a pair of [[Neurotyrant]]s at the Vaults of Repose. It was confronted by almost a score of White Templars [[Dreadnought]]s, who nearly all were sacrificed to hold the attack back as [[Colonel]] [[Uveda]] of the [[Ortegan Grenadiers]] launched a counterattack. When Chapter Master Starvo arrived, the Fiend of Hag Rift was badly wounded but escaped to fight another day.{{Fn|1c}}

Amidst these slaughters came the third Norn Emissary, who managed to emerge at the Konstantin Plaza where Leontus made his personal headquarters. In the ensuing chaotic struggle, the Norn Emissary was destroy a security gunship and surge towards Leontus before being struck town by [[Captain-General]] [[Trajann Valoris]] and his accompanying [[Adeptus Custodes]]. Valoris had arrived with reinforcements consisting of two Battle Groups of [[Indomitus Crusade Fleet Sextus]]. With Valoris at the helm, these new Space Marine and Custodian arrivals were able to launch a vicious counterattack. Not to be outdone, Tor Garadon aboard the still-fighting ''Phalanx'' launched a planetside [[Drop Pod]] assault of Imperial Fists to help drive back the Tyranids.{{Fn|1c}}

====Counterattack====
Valoris and his reinforcements were crucial in turning the tide, sweeping across the Formidyre system to drive back the Tyranids. He then focused on relieving the Pyremoat and Kastayl Systems, knowing that he still did not have enough resources to expend on the rest of the Sub-Sector. At Kastayl, the Tyranid siege was broken by the [[Raven Guard]], [[Blood Angels]], and [[Black Templars]]. At the Pyremoat Sanctuary, Space Marines from over a dozen chapters engaged the Orks under the Monsta-Boss. However by now, many worlds such as Rakhnor, Lembyq, and Vohyd had since been devoured of all organic life. In the Stanghalde, Irontower, and Gallospire Systems only a handful of survivors remained.{{Fn|1c}}

The war for the Bastior Sub-sector had been won, but at enormous cost to the Imperium. Moreover, Tyranid infestations in the region were still high and the xenos were replenishing their numbers at a terrifying rate. The Swarmlord was still at large at Sanctum, and Tyranids still harried Imperials on its surface. More reinforcements would be required to fully drive back the aliens.{{Fn|1c}}

===Imperial Order of Battle===
*[[Imperial Guard]] - Many [[Regiment]]s{{Fn|1c}}
*[[Militarum Tempestus]]{{Fn|1c}}
*[[Imperial Navy]] - Many flotillas{{Fn|1c}}
**Two [[Indomitus Crusade Battle Group|Battle Groups]] of [[Fleet Sextus]]
*[[Space Marines]] - Over a dozen [[Chapter]]s including:{{Fn|1c}}
**[[Ultramarines]]
**[[Imperial Fists]] - 300
**[[Black Templars]]
**[[Blood Angels]]
**[[Raven Guard]]
**[[White Templars]]
**[[Deathwatch]]
*[[Sisters of Battle]] - Several [[Order]]s including the:{{Fn|1c}}
**[[Order of the Bloody Rose]]
**[[Order of the Argent Shroud]]
**[[Order of the Ebon Chalice]]
**[[Order of the Valorous Heart]]
*[[Adeptus Mechanicus]]
**[[Skitarii]]{{Fn|1c}}
**[[Basilikon Astra]]{{Fn|1c}}
**[[Collegia Titanica]] including the [[Legio Destructor]] and [[Legio Abjuror]]{{Fn|1c}}
*[[Knight]]s
**[[House Terryn]]
**[[House Griffith]]
**[[House Taranis]]
*[[Adeptus Custodes]]
*[[Frateris Militia]]

===Sources===
*{{Endn|1}}: [[Leviathan (Box)]] Rulebook {{Cite Marker End}}
**{{Endn|1a}}: pgs. 230-233
**{{Endn|1b}}: pgs. 236-239
**{{Endn|1c}}: pgs. 242-253

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