Pyrathas (Fortress World)

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Pyrathas: Pyrathas was an Imperial Fortress World found within the Pyrathas Majorus System of the Jericho Reach. The system's primary star is a fierce, blue-white supergiant. This star is orbited by a second brown dwarf in a tidally locked orbit. Inside this brown dwarf's penumbra, Pyrathas also hangs in a tidally locked orbit, shielded from the fury of the supergiant. Its strategic location made it the second-largest (after Karlack) anchorage for the Imperial Navy in the Iron Collar.

The planet is marginally habitable and resource-poor and was ignored by the Imperium until Hive Fleet Dagon seemed like it might devour everything. It was believed that the glare of the system's primary would be enough to deter any Tyranid invasion. Thus, a colony was established on the surface, a place of retreat in case things went south.

A tendril of the Hive was indeed utterly devastated at Pyrathas. But rather than make the Tyranids stay away, it made them evolve. The next, larger tendril returned around the time of the Battle of Hethgard, fully adapted to the harsh stellar radiation.

The two Navy escorts protecting the place were quickly overwhelmed, as were orbital and plane-based defenses. Tyranids landed en mass on the surface, and all seemed lost. Then the God-Emperor interceded, the Tyranid Overmind was destroyed, and the Tyranids at Pyrathas lost cohesion, and the absorption of the planet's resources was halted.

Numerous feral Tyranid creatures continued to roam the planet for years. They were dangerous if provoked, but rarely worked in groups anymore, and could even be scared away with high noise and bright lights. By the 230s they had largely been eliminated by Marine Scouts proving their worth to the chapter.

Alphos (Fortress World)

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Alphos: Alphos was a human-inhabited world that was conquered during the first expansion phase of the Crusade. It was subsequently turned in to part of the Iron Collar, the ring of Fortress World protecting the Well of Night.

Alphos was only lightly defended during the Battle of Hethgard, but still managed to gain the upper hand against the Tyranid splinter fleet sent there. Something about Alphos made it very hostile to the invading Xenoforms, and more Tyranids died to the environment than to the guns of men. The invaders eventually adapted, and from a crashed hive ship a Tyranid synapse creature directed the remaining Xenos against the increasingly weak human garrison. The synapse creature was eventually eliminated by Barotta's new breed of Aurum marines, greatly reducing the Tyranid threat on Alphos. 

The searing hot sulfurous atmosphere makes Alphos a hell-hole, requiring heavy protective garments and breathers if you want to go outside, but it's vast mineral fields are too rich to be left idle, so the workers toil now, as they always have, stripping away one layer of rock to expose the next. The Adeptus Mechanicus did some preliminary terraforming studies, but the results were not promising, and the project was ended. Instead, a large number of Squat abhumans were moved here, as they are better suited to Alphos' harsh environment. 

Hive Fleet Hydra

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"Beastmaster" Taurus, the Last Black Raven, was briefly in mental communion with a Tyranid entity in 232.M42. The hive mind was searching for synapse creatures of the vanquished Hive Fleet Dagon, and Taurus' unique psy-bond to his Hive Tyrant steed let him catch glimpses of a vast, many-headed organism. He gave it the name "Hive Fleet Hydra." 

Since the hive mind was actively trying to figure out what had befallen Hive Fleet Dagon, it could be that Hydra is the master organism and that Dagon was but one of its many heads. The thought is sobering.

Fortunately, Hydra seemed not to be in Jericho's immediate vicinity, so it could be the sector still has a few good years before all life is consumed.

Research Option: Hive Fleet Hydra unlocked.

Credos (Devoured World)

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Credos was a Frontier World rich with promethium found within the Jericho Reach. For this reason, the Achilus Crusade established an outpost early on in the formation of the Orpheus Salient. 

Credos was the first Imperial world to fall to the Tyranids of Hive Fleet Dagon.

Phonos (Devoured World)

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Phonos was a Frontier World of massive mountains and vast forests, seemingly untouched by man, when the Achilus Crusade's scouts arrived here late M41. Untouched, until a single STC-compliant facility was found, Facility Phi-Omega-Nu-Omicron-Sigma, covered in impenetrable force fields. 

The Mechanicus erected a research base, Table Mountain, nearby, and proceeded to pour millions of Magi-hours into understanding the nature of the facility and how to unlock it. By the time the Tyranids devoured the world, the tech-priests had not succeeded.

Avalos (Devoured World)

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Avalos is a semi-Devoured World located within the Orpheus Salient. A major action against a Genestealr Cult was fought by the Deathwatch here, resulting in the death of the Broodlord and the exposure of a massive cult following. 

As the Inquisition was purging the unclean, a Hive fleet arrived, undoubtedly summoned by the Broodlord. The timely intervention of a small Imperial fleet, led by the battleship Emperor's Wrath, provided the Deathwatch with a means to lead a boarding action against the hive ship. To the honor of the Primarchs and the God-Emperor, the Deathwatch carried the day and managed to destroy the vessel's synapse chamber. This act threw the Tyranid invasion into disarray.

While the invasion was halted, countless Xenos did make landfall and caused considerable damage to the planet's biosphere. The clean-up will take generations to complete, but if enough resources are dedicated to the task, Avalos can once more be made into a prosperous human planet.

Treyen (Feral World)

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Treyen is an unremarkable feral world deep in the Orpheus salient. A largely temperate world, Treyen's scant population is centered primarily in the western hemisphere. The last Imperial census had the population at roughly 250,000 with an average technology level equivalent to that of the Bronze Age.

The system's primary star is entering into its last stages of life, and as such solar flares are beginning to spread a blanket of radiation around the planet. This stellar activity has a nasty habit of causing long-range vox transmissions to be unreliable and also causes void shield failures, but it also causes havoc for the Tyranids. For this reason Treyen was chosen to make a stand: this far, but no further.

The Battle of Treyen turned out to be both long and bloody but eventually ended in a resounding victory for the Imperium. It was the first major victory - and the last until Hethgard. What followed after Treyen was a period of silence, which the Crusade's leaders took for victory. It was not. Treyen had only been a single hive fleet. Many more came after.

Treyen is a pleasant enough place, with adequate resources. It could be colonized and civilized, and in a few decades provide the Sector with a steady stream of income.

Devoured Worlds of the Jerioch Reach

The Xenos menace known to the Imperium as "Tyranids" seeks out and devours entire worlds. They are primarily seeking biomass to expand their hive fleets, so they tend to go after worlds rich in life, but they will sometimes devour even marginal worlds.

In addition to biomass, Tyranids will regularly siphon a planet's atmosphere and liquid water. They've also been known to strip worlds down to the bedrock. Unconfirmed reports claim they are even engaging in primitive mining operations. On Ocean World [REDACTED] they cracked open the world's vast promethium reservoirs, letting it mingle with seawater before sucking the planet dry.

Killing an entire world takes time, even for the Tyranid swarm, years, decades even. Possibly longer if the swarm is smaller or the planet rich. A few Devoured Worlds are completely drained. Sometimes the Tyranids will move on before time. In other cases, they have been driven off or destroyed by Imperial forces.

Except in the rarest of cases, the planet is too damaged to continue to sustain life. The ecosphere is too damaged for it to recover - it's an extinction event, and the world will need millions of years to recover. The Imperium will routinely order Exterminatus for such half-devoured planets.

Devoured worlds in the Jericho Reach:

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Castobel: Unlike Vanir, Castobel was fertile enough to make it a juicy target for the Nids. The human defenders used scorched earth tactics and were able to hold out in several fortress-hives. They would not have been able to hold out forever, but the Hive Mind called away the besieging fleet to take part in the Battle of Hethgard.

Eleusis: Escaped mostly intact, when the Adeptus Mechanicus locked away the planet's waters, turning it into a forbidding dust-ball covered with heavily fortified mountaintop shrine-cities. Unknown to Crusade Command, the planet was already infested with Genestealers, which may have been the true reason it was passed over - the Xenos planned to come back later...

Freya: The remote mining world of Freya had little to attract Tyranids in the first place. When the Hive Fleet arrived, it consumed all human life, but otherwise left the system more or less alone.

Scansion Beta: The hive tendril that had consumed Themiskon had moved to this system at the time of the Crusade. Uninhabitable by humans, the system nevertheless contained a lush world, prime cut for the Tyranids. Lord Commander Ebongrave again ordered bio-terminators to be deployed, wiping out all life (nearly depleting the Crusade's stores of such weapons).

Themiskon Point: Formerly an Imperial Frontier World in the Canis Salient, Themiskon was already overrun by Tyranid bioforms by the time the Crusade forces reached it. Lord Commander Ebongrave ordered bio-terminators to be deployed, wiping out all alien life.

Vanir: Vanir was a human-held hive world. Poisonous and almost life-less by the time the Tyranids arrived, it wasn't exactly prime real estate. The Xenos slaughtered the vast human population, devouring them all, but didn't bother with anything outside the hive walls.

Castobel (Hive World, Orhpeus Salient)

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Castobel is a Hive World still ruled by a noble-born elite that remained loyal to the Imperium's ways through the long Age of Shadow. Not long after its rediscovery by the Achilus Crusade, Castobel faced the deadly threat from the encroaching Tyranid fleet of Hive Dagon. The final reports from before the battle of Hethgard indicated a full-scale Tyranid invasion, but the defenders holding firm inside their hives after torching the majority of their planet's biomass to prevent it from falling into Xenos' tentacles.

Castobel is bruised and battered, with more than 90% of its biomass destroyed by humans to deny it to the Nids. Only three hives survived until the coming of Barotta; one was targeted by Exterminatus, the second infested by Stealers, but the third proved true to the Empire.

Beastmaster Taurus, last of the Black Ravens, did much to ensure the continued survival of the Stealer-infested hive. The Inquisition maintains a close watch, but thus far there has been no sign of a stealer resurgence.