The invasion began 250 years after the last Tyrannic War and the destruction of the hive fleet Behemoth. An armed presence had been maintained in the galactic southeast, which members of Earth's Administratum began to question the need for, arguing that Behemoth had been the sum total of the Tyranid race. When worlds along the eastern fringe began to erupt in rebellion, terrorism, riots and sabotage, the same adepts claimed the people were dissatisfied with living amid an armed camp.
The Inquisition became suspicious of the adepts' dissent and their downplaying of the situation, and began an investigation, which established that all of the dissenting adepts had either come from the southeastern region or had travelled there at some time. This was the only link between the members that could be found, and some had never even met each other. Inquisitors were also deployed from Talasa Prime to investigate the planets of the Ultima Segmentum who were displaying their anger.
Purges were made within the Imperium, especially on Terra, focused on suspected traitors, who had had contact with the Eastern Fringe. Tens of thousands of suspected traitors were sent to prison colonies.
The Herald of the Kraken, the Ichar IV Rebellion
The Imperium had several concerns about the uprisings. One of them was a planet named Ichar IV. It was vital to the operation of the eastern region as its huge factories form the centre and lynch pin of one of the few densely populated sectors in the Ultima Segmentum. The entire planet had been seized from the control of the Imperium by a religious fundamentalist group named the Brotherhood. Years before, they had captured the hearts and minds of the population of the planet by preaching the return of the Emperor and promising better times to come. This is the sort of promise that was sought by the workers of the factories after a life with no power or freedom. The Brotherhood quickly set up missions and chapels throughout the poor regions of the planet. The Ecclesiarchy monitored the Brotherhood for any signs of corruption or heresy, but none could be found. Eventually, permission was sought and granted for the construction of a Brotherhood cathedral in Lomas, the biggest city on Ichar IV. Shortly after the completion the trouble began; the Brotherhood refused to pay its tithes to the Planetary Governor and would not allow its members to be inducted into the Planetary Defence Force. Preachers whipped the population into a frenzy, saying the Emperor would return soon. Brotherhood militias began to roam the streets, punishing more "unbelievers" than actual criminals.
Things reached a peak when rioting broke out during a mass demonstration outside of the great cathedral. Arbitrators of the Adeptus Arbites moved in with power mauls and suppression shields but were fired upon from the cathedral. The Arbitrators returned fire and killed several of the Brotherhood militia. This enraged the mob and they surged forwards several times, eventually forcing the Arbitrators to fall back, especially as another, larger mob had just arrived to support them. Rioting then spread throughout the planet and most of the forces of the Arbites were forced back. When the Planetary Defence Force was called for, most rebelled and joined the ranks of the Brotherhood. Eventually, news of the assassination of the Planetary Governor reached the public and vicious fighting broke out in all of the cities of the planet. Within hours, tanks decorated with revolutionary banners were seen driving down roads in cities, pushing the Arbites back. With dawn, news of the assassination of the governor and most of his ministers had spread over the entire planet, and the Brotherhood quickly seized control of several broadcasting stations, announcing their new theocratic state.
The Arbites still held control of the majority of the countryside and the Arbites fortress at the centre of Lomas. Most of the cities had been captured by the Brotherhood, denying the Arbites vital resources. Inquisitor Agmar arrived twenty seven days after the rebellion, on the same day that the fortress was overrun by Brotherhood forces. Most of the Judges in the fortress escaped however, moving to take control of the four main power stations of the city. Inquisitor Agmar saw this as much more of an organised rebellion than a sporadic outburst of feeling. He called for the support of the Ultramarines to help retake the planet. While the Imperial forces waited for the arrival of the Ultramarines, they bombarded the cities and pushed back vicious assaults by militia battalions. Repeated attempts to reach the power stations failed and, six days after Agmar arrived, they detonated several Melta Bombs, completely destroying the generators.
Now the war took on a long, grinding city fight with casualties spiraling upwards daily. Every doorway could have had a booby trap and there were snipers dotted around all over the cities. Entire Imperial Guard patrols disappeared without trace in the maelstrom. This was the same across the planet as the Brotherhood held the armouries of the Imperial Guard and had plenty of people to draw on to become soldiers. Inquisitor Agmar led several small forces into Lomas to uncover the nature of the Brotherhood. He was slowly piecing together the story when, in a chance raid, he slew a Neophyte of the Brotherhood and saw what manner of creature was leading the revolt. Agmar sent a message confirming his fears of another invasion, to the Inquisition and awaited the Ultramarines.
Thirty nine days after the rebellion began, the Ultramarine battle barge Octavius entered orbit and deployed its drop pods. The planetary defences were largely inactive due to the damage to the generators and as such landing casualties were light. Space Marines secured the armouries and Governor's palace and fought off several poorly organised counter attacks, causing massive casualties. Outside, the Imperial Guard launched massive attacks to link with the Ultramarines, using their Leman Russ Battle Tanks as moving strongpoints and the Brotherhood lines bent back.
More than twenty Space Marines in Terminator Armour teleported into the chapel and destroyed the chapel defenders after Agmar sent a message to the Octavius via spy satellite. More guards appeared from side doors and a storm of lasbeams and autoshells ripped out, massacring many of the guards, but not before several of the Terminators were dragged down. The Terminators' single heavy flamer proved to be invaluable, its flames incinerating the unprotected assaulting forces. Some of the Neophytes were striking out with inhuman speed and terrible claws.
The Terminators then spread out and searched for the myriad of secret passages there must be. They soon found one under the altar, and the altar was quickly removed. As they moved down into the crypt, they heard the clattering of claws on stone. As the creatures jumped into the lights of the Ultramarines, they were identified as Genestealers. This showed the Inquisitor's belief that there was a coven at the heart of the revolution to be correct. The battle began and raged for a long time. Hundreds of Genestealers died, piling up on top of each other. Eventually, the horde's numbers were spent in their attack. Several Terminators had been killed as their armour was torn open by the inhumanly sharp claws of the Genestealers. The remainder moved further into the crypt without encountering more of the creatures. Deep beneath the city they found a huge cavern where the huge and bloated great grandfather of the brood, the Genestealer Patriarch, sat. As the Terminators approached, another horde of Genestealers intent on protecting the great father, attacked the Terminators from out of seemingly nowhere. Storm bolters rang out, resulting in carnage. The Chapter Librarian fought his way to the dais but the Patriarch used its psychic powers to attack the Librarian. A surge from the psychic hood broke the spell and the Librarian forced his body out of the real world for an instant and then he reappeared, teleported onto the dais. The creature lashed out and blood and sparks flew from the Librarian, but the Patriarch easily parried the return blow.
The Librarian called on his battle-brothers and the dais was swept with bolter fire. Some shells struck the armour of the Librarian but the Patriarch was also wounded. The Librarian used this opportunity to strike with his force axe, the Librarian's own psychic power behind the blow allowing the weapon to tear through the tough hide of the Patriarch. The Patriarch was dead, suddenly leaving the brood and the entire revolution leaderless. The revolution felt the death of their leader and lost its impetus and cohesion. The remaining Terminators slew the rest of the Genestealers and the battles above stopped mostly as the revolutionaries could only retrench themselves. Small groups of Acolytes and Neophytes held their positions in bunkers and towers but were soon destroyed by the tanks and heavy fighting vehicles of the Imperial Guard.
Ichar IV was back under the control of the Imperium and all remnants of the Genestealer Cult - the Genestealers, hybrids, infected humans, cult members and traitors - was ruthlessly wiped out. Inquisitor Agmar, leading the Ultramarines, methodically purged the planet, which eventually returned to normal. There were still questions that remained unanswered. One was the fate of the human leader of the Brotherhood, as his body was never found. The second was that the Astropaths had reported a shift in the warp, distant still, but the oldest of the Astropaths had sensed the call of the Patriarch and felt the change in the warp. He had sensed something vast and shadowy, a monstrous entity which had turned its attention to Ichar IV.
Agmar then reported to the Inquisition, including a report on survivors fleeing from the outer regions, but it was clear to the Inquisitor, the Tyranids were back with a new Hive Fleet, Kraken. In the confusion and rebellion, planets in Kraken's path were easily consumed.
The Battle of Ichar IV
As Kraken approached Ichar IV in 992.M41, devouring hundreds of planets in its path, thousands of Genestealers burst from underneath the surface of the planet, giving lie to the claims that the Genestealer infestation had been purged years earlier. As confusion reigned and Imperial defenses were overrun, massive amounts of Tyranids landed on the Hive World. These included not only Gaunts, Warriors, and Carnifex's but also larger creatures like the Tyrannofex and Hierophant Bio-Titans. The Tyranids were throwing everything in their disposal at Ichar IV.[5a]
However all was not lost. Forewarned due to the previous infestation, the Imperium was able to count a strong defense of the system and inflicted heavy losses on the Tyranids. The Imperial defenses were significantly bolstered by Marneus Calgar, Lord of the Ultramarines and a hardened veteran of the Battle for Macragge, who led both his own and allied Space Marines against the Tyranids once more. Using tactics he had developed in the First Tyrannic War, Calgar rallied the defenders of Ichar IV and cast the Tyranids from the world after a vicious struggle. In a replay of history, Calgar again faced the Swarmlord as he had during the battle for Ultramar. This time however it would be Calgar who emerged triumphant, slaying the beast in an epic duel. Without the Swarmlord to counter Calgar's strategies, the Tyranids were cast from the world. However victory was a shallow one, as Ichar IV lay in ruins. Worse still, allies of the Ultramarines, the Scythes of the Emperor and Lamenters, were all but wiped out.[5a]
The Battle for Iyanden
In 992.M41  the Eldar Craftworld of Iyanden suffered its greatest tragedy at the claws of Hive Fleet Kraken. Around the same time that one tendril of the Hive Fleet was assaulting Ichar IV, another was approaching the Craftworld, one of the largest and most populous of the Eldar. The first physical proof that the Tyranids were approaching was reported by Iyanden's Ranger's, who gave word of a swarm of immense proportions was heading directly towards the Craftworld. The Tyranid fleet was too vast to outrun and Farseer Kelmon, the spiritual leader of Iyanden, declared that all would have to fight together if they were to stand any chance. The entire Craftworld was fortified, every Eldar citizen was to be deployed as Guardians, and in a sacred ritual the Avatar of Kaela Mensha Khaine was awoken. Reluctantly Farseer Kelmon ordered that the Craftworlds Wraithguards, constructs inhabited by the souls of dead Eldar, be awoken.[5a]
The first Tyranid swarms attacked Iyanden just twenty days after the Rangers had first brought word. By that point, the world had been isolated for a week by the Shadow in the Warp. The immense Tyranid fleet of Bio-ships approached the Craftworld by the tens of thousands, attacking at first in random waves. The defending Eldar fleet at first destroyed each wave, but was slowly being overwhelmned by sheer numbers. Before the exhausted Eldar fleet could catch a breath, it was hit by huge two waves in quick succession by a swarm of Bio-ships that dwarfed all the others combined. The Eldar fleet was swept aside and the Tyranids began landing on the Craftworld itself in Mycetic Spores. Huge battles soon erupted all over Iyanden's skies, fields, and corridors. Striking Scorpions did battle with Hormagaunts, Carnifex's wrestled with Wraithlords, Dire Avengers exchanged fire with Termagaunts, and Falcons engaged in bitter dogfights with Harpies and Gargoyles. War waged beyond the Materium as Warlocks engaged in psychic duels with Zoanthropes. Soon the Tyranids managed to land Hierophant Biotitans which did battle with the Craftworlds own graceful Phantom Titans. The battle was fierce and though the Tyranids took heavy losses, slowly the Eldar defenders were being worn down in a titanic battle of attrition. As the Shrine to Asuryan was being ravaged by the Tyranid hordes, the doom of Iyanden seemed certain.[5b]
Meanwhile, word of Iyanden's peril managed to reach Prince Yriel. Though Yriel had vowed to never return to the Craftworld after being stripped of his rank decades earlier, the Corsair Prince could not abandon Iyanden in its darkest hour and his fleet sped towards the battle.[5b]
Yriel's forces arrived at Iyanden just as it stood on the brink of extinction. His fleet thrust into the Tyranid bioships and as an admiral without peer, Yriel's ships combined with the surviving Iyanden vessels to rip the heart of the Tyranid swarm in space. Preventing any more Tyranids from landing on the surface, Yriel managed to beat back two vicious Tyranid counterattacks before the space-borne Hive Fleet had been defeated. However the battle on the ground was still desperate, and Yriel sped towards Iyandens surface to personally take command.[5a]
Though the Tyranid space fleet had been defeated, on the ground the Eldar defense had been all but broken under a suicidal onslaught by waves of Tyranid beasts. A massive Hive Tyrant led the frenzied horde, butchering all in its path and appearing to be all but invincible to Eldar fire. Amidst the carnage, the Avatar stepped forward, the only warrior capable of slaying a Hive Tyrant. Roaring a challenge to the beast, the Avatar sought to engage it in single combat. However the Tyranids do not fight for honor and it is doubtful that they even have any concept of bravery or corwardice. Instead of meeting the Avatar in single combat, the Hive Tyrant summoned a dozen Carnifexes to overwhelm the iron-clad warrior. With the Avatar lost, the last vestiges of hope ebbed from the Eldar. But, in an act that restored Yriel as a hero for his people for all eternity, the Prince finally arrived to reinforce the wavering ground troops. The Tyranids were on the verge of overrunning the final line of defenses when Yriel himself plunged into the fray wielding the cursed Spear of Twilight, an ancient weapon of such power that it eventually burns out the life-force of any who wields it. Yriel was willing to sacrifice his immortal soul to fight the Tyranids.
The monstrous Hive Tyrant turned to meet the Eldar prince, but proved no match for the energies of the Spear of Twilight. With one fluid motion, Yriel thrust the weapon directly through the head of the creature. With their commander lost, the Tyranids ceased to attack as a united wave and reverted back to their basic instincts. The scattered alien invaders were able to be systemically isolated and destroyed by the remaining Eldar defenders. Iyanden had been saved.
However the victory of Iyanden was a hollow one. Though they had emerged victorious, they had only done so at a terrible cost. Iyanden stood in ruins and four-fifths of its population lay dead, including Farseer Kelmon. Its majestic fleet had been reduced to a pititufl shadow of its former self and its landscape ravaged. Worse still, the very souls of those spirit stones that had been destroyed by the Tyranids were lost forever. Thus, Iyanden would never recover from the devastation. The Eldar had learned a painful lesson and would never again underestimate the Great Devourer.
With the defeats at Ichar IV and Iyanden, Hive Fleet Kraken splintered and its remnants moved towards the Galactic Core.[5a] However this was not the end of the Tyranid menace, for they would be followed by the even larger Hive Fleet Leviathan. In addition, Kraken's splinter fleets and remnants continued to ravage parts of the Galaxy.
- The Battle of Hollonan - In response for a request for assistance in putting down a seemingly minor rebellion, Chief Librarian Mephiston of the Blood Angels would lead a strike force to the Imperial Hive World of Hollonan. However what was first thought to be a minor rebellion is soon revealed to be a massive infestation by Tyranid Genestealers of a splinter fleet of Hive Fleet Kraken. Though they manage to purge the alien infestation, the Blood Angels are too late and the invasion of Hollonan by Tyranid Bio-ships is already underway. Realizing the gravity of the situation, Mephiston sends requests for aid to the Angels Vermillion Space Marine Chapter.[4g] In the ensuing battle waves of Tyranids manage to overrun both the planetary defense batteries and fusion reactors. Only where Mephiston fights do the forces of humanity hold in a vicious two week battle. Managing to personally slay the Hive Tyrant, Mephiston himself is struck down by a Trygon in the process. As the battle seems increasingly desperate, fresh companies of Blood Angels and Angels Vermillion emerge from the sky in Drop Pods and Stormraven Gunships. The forces of humanity are further aided by the Eldar of Ulthwe Craftworld under Farseer Eldrad Ulthran, which has chosen to temporarily ally with the Imperium for their own mysterious reasons. Caught between the 3 armies, the Tyranids are crushed. Eldrad remains just long enough to see Mephiston recovered by the rubble before the Space Marines and Eldar go their separate ways.
As Hive Fleet Leviathan emerged, a remnant of Kraken that had been thought lost in a Warp Storm returned, apparently attempting to fuse with Leviathan. Had they done so, the bio-information gathered by Kraken could have been used with Leviathan's resources to create a new mighty strain of Tyranid. Fortunately, this remnant of Kraken was defeated at the Battle of Duriel.
The creatures of Hive Fleet Kraken have a colouring pattern of bone skin with red carapaces and usually bone or black weapon symbiotes.
- 1: Codex: Tyranids (2nd Edition)
- 2: Warhammer 40,000 3rd Edition Rulebook
- 3: Codex: Tyranids (3rd Edition)
- 4: Codex: Tyranids (4th Edition)
- 5: Codex: Tyranids (5th Edition): pp. 23-25
- 6: Codex: Eldar (4th Edition) p. 52-53
- 7: Orphans of the Kraken (Short Story)
- 8: Codex: Blood Angels (5th Edition) pg.17
- 9: Warhammer 40,000 6th Edition Rulebook pg.175
- 9: Codex: Tyranids (4th Edition), 2004, p 59
- 10: Iyanden: A Codex: Eldar Supplement (E-Book) pg.45-47
- 11: Codex: Tyranids (6th Edition) (E-Book Edition) - Ichar IV