Chapter 259: The Cosmic Rust Cannon

"No! Ironhide!"

"Damn it, Sentinel, what has gotten into you?!"

"You killed Ironhide! You murdered our comrade!"

Across the military yard, the Autobots snapped out of their stupor, shifting their limbs into heavy cannons and energon blades, aiming directly at Sentinel Prime.

Even the garrison soldiers, running in from the outer gates, scrambled to mount rocket launchers on their shoulders, forming a tight ring around the rogue commander.

Surrounded by a dozen primed barrels, Sentinel didn't flinch. He looked past the weapons as if the soldiers and Autobots weren't even there, tilting his head toward the open air beside the transport:

"Decepticon, I have delivered my tribute in blood. Do you still intend to lurk in the shadows?"

"What? Decepticons?!"

The Autobots and Mearing's detail froze once more.

"Did they track us here?"

"Weapons up! Watch your flanks!"

"Hold on, what did he mean by a tribute? I have a bad feeling about this."

"Has Sentinel been working with the Decepticons this entire time?"

"He was the supreme commander of the Autobots... how could someone of his stature fall so low?"

Amidst the shouts, the air beside the supply depot rippled like heat over pavement, slowly fading away to reveal a massive, heavily armored warrior.

"Skygnaw!" Lennox gasped, his blood running cold as he recognized the mech who had appeared from nowhere.

Skygnaw cast a calm glance across the courtyard before turning his crimson optics onto Sentinel Prime.

"Sentinel Prime, humans have a saying about leaving the shadows to embrace the light. I have already forwarded telemetry of your actions to Lord Megatron."

"On behalf of the Decepticon high command, I welcome your return."

As one of the two active Primes within the Decepticon ranks, Skygnaw held every right to speak for their forces.

Still, watching a former Autobot supreme commander walk into the enemy fold, with Skygnaw framing the betrayal as an awakening, left everyone in the yard stunned.

"So you are the warrior Megatron spoke of—Skygnaw?" Sentinel regarded him with a guarded gaze, his optics narrowed.

"I am."

Skygnaw kept his expression flat. It was clear that the moment Optimus revived Sentinel on the Moon, the old commander had established private communications with Megatron, keeping everyone else in the dark.

Soundwave had likely known the parameters of the plot from the start, treating Skygnaw as a blunt instrument to draw out the garrison.

Yet none of them realized that Skygnaw already knew every move before the board was even set.

Sentinel looked aged and weathered, but he carried himself with an imposing, cold authority that outstripped Optimus Prime's restraint. He was a veteran who moved with absolute conviction.

In the original timeline, whether because Optimus held back against his former master or because Sentinel was simply that formidable, Sentinel had thoroughly dominated their duel.

Skygnaw shifted his focus down toward the heavy, wide-bore firearm held firmly in Sentinel's right servo. A knot of caution tightened in his processor:

That is the Cosmic Rust Cannon.

Skygnaw had arrived at the perimeter well before the transport stopped, watching the entire ambush unfold, including Sentinel's shot into Ironhide's chest plate.

The Cosmic Rust Cannon was one of Sentinel's signature weapons, forged in the ancient eras of Cybertron.

Its chassis was lined with exposed conduits and power indicators. While it looked like a standard heavy rifle, its payload was horrific to any mechanical being.

Instead of a conventional beam or kinetic slug, the weapon fired a concentrated stream of microscopic, metallic-consuming microbes.

These organisms served a single function: the rapid, unchecked corrosion of Cybertronian alloys.

The microbes chewed through armor and internal circuitry within seconds, reducing advanced metals into brittle, rusted flakes.

One had only to look at Ironhide. The veteran warrior no longer possessed a recognizable frame; on the asphalt lay nothing more than a pile of rusted slag and crumbling red-brown debris, looking like scrap iron dug up after centuries underground.

The horrifying speed of the corrosion proved how lethal the weapon truly was. Conventional armor offered no resistance, and once the infection took hold, the decay was practically irreversible.

Skygnaw noticed the heavy barrel of the cannon was tilted slightly in his direction, held at the low ready.

Sentinel was under no illusions about his new allies. Partnering with the Decepticons was walking a razor's edge, and he remained deeply suspicious of another Prime standing in front of him.

"Sentinel Prime," Skygnaw said, breaking the silence with a wave of his arm.

Behind him, Grindor's massive form stepped into view, securely carrying five crystalline rods across his chest.

"These were recovered under Lord Megatron's orders. Now, let us see your part of the bargain."

Skygnaw had diverted his flight to raid the Autobot staging ground because Megatron had messaged him mid-transit. The latest transmission had instructed him to hand all five pillars directly to Sentinel.

Seeing the pillars, the Autobots and Mearing's team felt their hearts sink even further.

They realized the base on Diego Garcia had already fallen under attack.

The situation was spiraling entirely out of control, yet with two Primes standing in the center of the depot, nobody dared to pull a trigger.

Skygnaw didn't reveal that he knew how to interface with the pillars. He simply motioned for Grindor to hand them over.

Taking back his creations, Sentinel showed no joy. He stood silent for a few seconds before speaking in a low, gravelly voice:

"Tell Megatron I will honor our pact. But I require preparation time."

"How long?"

"Three solar cycles."

"Very well. Lord Megatron is en route to this world. Ensure everything is in place before he arrives."

"He will have his gate," Sentinel scoffed.

With a sweep of his arm, the five pillars lifted from the ground, hovering around his chassis as if gravity no longer applied to them.

Skygnaw raised an eyebrow plate. He had studied the pillars, but controlling them with a mere gesture showed an innate mastery that only their creator possessed.

Still, opening a bridge capable of pulling an entire world across light-years required immense energy and coordination.

Unless...

"Sentinel, what are you doing?!"

A sharp, furious shout shattered the tense air.

Mearing stepped out from behind an armored truck, her face flushed with rage as she pointed an accusatory finger at the ancient Cybertronian.

Any lingering hope that this was a misunderstanding had vanished. Hearing Sentinel coordinate terms with Skygnaw pushed her past her breaking point.

"Foolish creature," Sentinel rumbled.

He hadn't bothered to explain his vision to Ironhide, let alone an insignificant human official.

Without aiming, Sentinel swung his heavy rifle toward her position and squeezed the trigger:

"I am Sentinel Prime. You do not demand answers from me!"

BOOM!

"Director, get down!"

Lennox threw his entire weight forward, tackling Mearing behind the wheel well of an armored SUV.

The soldiers standing directly in the firing line weren't fast enough. The concussive blast caught them point-blank, dissolving their gear and burning through the line in a wave of searing heat.

The weapon might have been designed to rust Cybertronian alloys, but a high-temperature concussive discharge was just as lethal to organic matter.

"Return fire! Suppressive fire!"

Lennox shouted as he pulled Mearing behind the reinforced plating of the engine block. "Director, our weapons can't scratch them! We need to pull back right now!"

Mearing, her hair disheveled and her coat covered in grit, looked up at Lennox, then toward Sentinel, who had already lowered his weapon with complete indifference. Without saying another word, she turned and retreated under the escort of her agents.

Sentinel holstered his rifle, turning his optics toward Skygnaw. "Handle the cleanup."

"Naturally," Skygnaw replied with a dry nod.

Leaving me to cover your retreat? Think again, Skygnaw thought.

Sentinel shifted back into his heavy rescue tender, his engine roaring as he broke through the perimeter gates. Not a single Autobot moved to pursue him, held back by the memory of the rust cannon and the imposing figure of Skygnaw still standing in the yard.

"Skygnaw, did you hit our home base?!" Bumblebee raised his arm cannon, his optics blazing with fury.

Skygnaw didn't bother answering. Anger was cheap on a battlefield; if fury could pierce armor, the Autobots wouldn't be standing frozen behind their barricades.

Before departing, Skygnaw took one last look at the pile of rust that had been Ironhide.

Sentinel's decision to eliminate Ironhide first was tactically sound.

As Optimus Prime's second-in-command, Ironhide not only served as a personal vanguard, but held operational authority to lead the ranks in Optimus's absence. Removing him dealt a devastating blow to Autobot morale.

In war, breaking the spirit of the enemy was paramount.

Furthermore, Ironhide's heavy plating and firepower made him one of the few combatants outside of the Aerialbots capable of mounting a stubborn defense. Sentinel had only one chance to strike from the blind side, and he had chosen the highest-value target in the yard.

Diego Garcia, Autobot base.

The red and blue semi-truck rolled through the shattered gates, coming to a halt on the scarred runway.

Optimus Prime had received the distress call mid-flight, but seeing the burning hangars and fractured barricades with his own optics weighed heavily on his spark.

Wreckage and scorched earth covered the entire installation.

"Optimus, you're back!"

Ratchet and Jolt were working tirelessly over wounded comrades, calling out as their leader stepped down from his cab.

Silverbolt was the first to approach, his expression solemn. "Do not blame yourself, Optimus. The Decepticons struck while our defenses were stretched..."

Cybertronian culture held little reverence for rigid hierarchy; though Sentinel had mentored Optimus, and Optimus had guided Silverbolt, they spoke as equals bound by duty.

Learning the details of the raid from Silverbolt, Optimus knelt beside several critically damaged soldiers, his faceplate heavy with sorrow.

His departure had not been a tactical misstep or a response to an enemy feint; it had been an unfortunate coincidence.

Today was the scheduled logistics run to ferry supplies to the Ark in orbit. Usually, with the Decepticons keeping a low profile, the Wreckers handled the transport run aboard the Xanthium on their own.

Yet with Skygnaw and Shockwave active again, Optimus had accompanied the crew into orbit to ensure the cargo arrived safely, leaving the base exposed.

"Those cursed Decepticons... Skygnaw will pay for this!"

The Wreckers descended from the shuttle ramp, their weapons clattering in shared outrage. Because human personnel monitored the staging grounds, Leadfoot, Roadbuster, and Topspin rarely loaded supplies inside the main perimeter, operating from remote pads instead.

"Optimus, they took the five pillars as well," Silverbolt added quietly. "They knew exactly where they were kept. Skygnaw pinned us down while Grindor secured the vault."

Optimus rose slowly, taking in the news. Over thousands of cycles of civil war, he had seen forward outposts overrun countless times.

Before he could give orders to secure the wounded, the screech of tires echoed across the access road.

Screeech—

Three sports cars—crimson, yellow, and silver—drifted onto the tarmac, rolling to a hard stop.

"It's Bumblebee, Dino, and Sideswipe!"

"Weren't they assigned to escort Sentinel? Why are they back so soon?"

"Wait... where is Ironhide? Did he stay behind to guard Sentinel's position?"

Bumblebee transformed smoothly, walking toward the gathered Autobots with heavy steps. In his hands, he carried a pile of crumbling, rusted metal fragments, setting them down gently onto the concrete.

"Bumblebee, what is this?"

The Autobots gathered around, murmuring in confusion. Only Ratchet took a step back, a look of horror dawning in his optics as he recognized the faint traces of the chassis.

Bumblebee said nothing, merely shaking his head with his faceplate cast down.

"Bee, talk to us! What happened out there?!"

Sideswipe stepped forward, his blades lowered, his voice raw and unsteady:

"Optimus... Sentinel Prime has betrayed us. He aligned with the Decepticons."

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