The Emperor’s Angel of Death

As Storm Claw Squad bombarded the massive Bio-Titan, the black Nightwatch descended, its hatch opening before it even landed. A Space Marine from the 10th Company stood inside, firing a heavy bolter into the swarm, shouting, "Get in here!"

"Go!"

The four quickly jumped into the transport. Before the hatch could close, the Nightwatch ascended rapidly. Less than two seconds after it had left its initial position, a wave of maggots, coated in slime, splattered across the ground. Upon impact, these creatures released torrents of acid and toxic substances, corroding the ground into a pit nearly ten meters wide.

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The Titan, having missed its target, roared in fury but was helpless, forced to watch the Nightwatch disappear. It then turned and began moving towards the Saint's Crown Mountains.

Boom————

Suddenly, a dozen Thunderstrike guided bombs detonated nearby, several striking it directly. The melta warheads pierced its thick carapace, causing tremendous explosions within the Bio-Titan. Amidst clouds of red vapor, the massive creature wailed, collapsing like a broken toy, its limbs severed.

"Chapter Master, the 10th Company has destroyed the Titan's hatchery and reported several Titan bioforms not found in the records."

Inside the command center, Sorshyan, who hadn't rested for ten days and nights, received the data-slate and reviewed the text report and visual information.

The report highlighted the Tyranid Bio-Titans and the Lictors that had evolved the ability to leap, as well as the massive, tank-like creatures covered in ultra-hard armor.

In the past ten days, the forward outposts had reported over twenty undocumented Tyranid bioform variants. In other words, the Hive Mind was constantly evolving in response to human defensive strategies, almost on a daily basis. Its tactics might have been somewhat rigid, but its methods were the most adaptable Sorshyan had ever encountered.

"Forward these detailed bio-reports to the Mechanicus Adepts. Have them registered in the Tyranid biological data archives, emphasizing the characteristics of these creatures."

"Yes, sir."

At that moment, Farzad entered the command center.

"Chapter Master, the toxic fumes are intensifying, nearly reaching the outposts. I fear our soldiers' protective masks won't hold up."

Sorshyan glanced at him and calmly asked, "What is the situation at Outpost Four?"

"Defense is holding, but ammunition needs rationing. Because we're at the lowest altitude, the fumes are approaching the perimeter walls."

"Altitude is irrelevant."

Sorshyan led him to a screen, beckoning to a nearby Tech-Priest, who transmitted an image. The screen flickered, revealing a cloud of pale yellow gas. Within it emerged a grotesque being.

It stood roughly three adult humans tall, appearing gaunt, covered in plate-like chitinous armor. Its forefront was a Tyranid head with a lower face entirely of tentacles. Its limbs were also tentacle-like. Protruding from the thick armor on its back were chimney-like structures, constantly emitting billowing pale yellow fumes. When it moved, it appeared to float, somewhat like a Norn Queen, but it had a strong tail for support.

"It's related to this."

"This is..."

"The Bio-Savants have tentatively named it the 'Toxic Fume Fiend'. It's responsible for most of the spore clouds. If we hadn't chosen a high-altitude position, we'd already be engulfed. But now the ground is almost entirely covered. The Tyranids have adapted the fumes, making them 'lighter', hence the current situation. These Toxic Fume Fiends are cunning, hiding in the fumes, rarely visible. Accurate targeting is difficult, and their numbers are significant. Their ability to fly makes them terrain-independent, making them troublesome. The Tyranids have more cards to play, but I'm running low on them."

Hearing Sorshyan's words, Farzad, known for his courage, couldn't help but show concern.

"What should we do now?"

Sorshyan turned to him, saying something unexpected.

"Return and organize the evacuation of Outpost Four immediately. I'll provide air and artillery cover."

"What!? Evacuate? Our defenses are holding..."

"They are now, but... Magos Cornelius Medici, can you come here for a moment?"

Hearing Sorshyan's summons, the xenos researcher from Ulannhudar rapidly approached on his mechanical limbs.

"What is your command, sir?"

"Tell the Captain of the Third Company about these Tyranid spore clouds."

The Bio-Savant extended a mechadendrite, inserting it into a nearby cogitator. The screen displayed a series of numbers and images, showing people struggling and festering.

"...Recent research indicates that the Tyranid spore clouds actually conceal an extremely complex biophage. Its sophistication is beyond words. It resists most immune responses. Brief exposure causes even Astartes nausea and uncontrolled muscle spasms. If a mortal is unfortunate enough to be exposed for over thirty seconds, the biophage takes hold. It replicates at an astonishing rate, spreading throughout the victim's system, breaking down organs and tissues, causing the victim to drown in their own froth and infected fluids. Worse, these microorganisms proliferate excessively in enclosed spaces, preventing even those in protective gear or power armor from escaping unscathed. They first clog filtration systems, then slowly seep in, attacking the victim. At high enough concentrations, they can fill ventilation systems, corrupting air purifiers."

"What is the current concentration?"

The Bio-Savant didn't give a specific value, but said tactfully, "The concentration around the Saint's Crown Mountains is extremely high."

Sorshyan nodded slightly.

"Thank you for your explanation, Magos. Continue your research. The warriors have brought back new variant samples."

"Yes, sir."

Sorshyan then looked at Farzad.

"This is the situation. We have no way to counter the Tyranid fumes. The planet's atmosphere will soon be destroyed. Our only option is to delay. Snow Palace is still safe at its current altitude. At the current rate of fume ascent, we can hold out for fifteen days."

Farzad nodded, then hesitated and said cautiously, "What if, after those fifteen days..."

Sorshyan said nothing, simply raised his chin with his hands behind his back.

"Go and execute the evacuation order."

Farzad snapped to attention, saluted sharply, and quickly ran out of the command center.