[Alert: Large amount of organics detected. Existence is endangered.]

That was the first time Custodian had heard of this warning, but it already had plenty of contingency plans prepared in the event a crisis such as now would occur. Except…

“I… only have one combat drone here…” Custodian concluded as it stared at its only standing ‘army’, a recently completed prototype spider combat drone.

‘All drones, initiate Alpha contingency plan. Return to the core room to prepare,’ Custodian ordered through the hivespeak, reaching every automaton linked to Custodian immediately.

As the A.I. prepared bio-iron weapons for the drones, it checked where the source of the alert was from. Three metallic figures covered in fur were running across the rocky floor from a horde of rats. There were different types of rats; small and big, old and young. But it didn’t matter to Custodian. What mattered was that these organics had to go, it couldn’t afford to lose three of its most important drones to some pesky organics.

‘I see you three found the spawning ground of the rats,’ Custodian spoke to the trio explorers.

‘Affirmative. However, now is not the time to commend us, Master Custodian,’ replied Ratslayer through hivespeak.

‘Can you try holding them out? It might be possible that the organics were simply agitated by your presence. If you show that you aren’t worth dying for, they might run back to their spawning ground,’ Custodian suggested.

‘That is possible, but right now, there’s too many organics for us three to handle only,’ Ratslayer answered.

‘Find a narrow path and hold them out. Use the two prototypes at will,’ Custodian ordered.

While the last three drones were being chased, the seven other drones gathered at the core room. They started equipping themselves with spears and shields, while the basket drones were converted to act as mobile barricades, which was easy to do since all Custodian had to do was remove the basket and replace it with a slab of bio-iron.

‘Hold them out at the outer slime hunting ground. Erect defenses all the way to the core room. You all have one directive: Exterminate all organics identified as Rats,’ instructed Custodian.

Six drones left to take their designated position along with their militia squad of carrier-turned-barricades. Though not as experienced as Ratslayer, Custodian expected the rest of the drones to be able to hold their ground. If all else fail, all ten drones would be returned to the core room, then the place would be sealed shut.

Organics are simple beings after all. If the threat to their home and safety is gone, they would obviously return to where they came from. But, Custodian wanted to see if it could fend off a major threat first. After all, even in failure, it could be a good learning experience for the A.I., or so it thought to itself.

At the inner rat hunting ground, the three explorers were defending a narrow passage against the rats, hoping to buy time or drive the rats back. As the pile of body rise higher, the idea that the rats would simply leave was starting to become nothing but a pipe dream.

“There!” Drone 8 shouted at they pointed at a direction, causing the two spider-like combat drones attached to their bigger kin’s chest to launch an attack as designated. They jumped off Drone 8’s torso, sped through the floor, slashed at the rat with unbelievable precision, then jumped back onto their older brother’s torso.

Drone 8 figured that if it could micromanage the combat drones, they would perform much better than letting them roam around by themselves.

‘Interesting…’ Custodian noted as it observed the battle. The A.I. turned its attention at its combat veteran, Ratslayer. He was sweeping the floor with his spear, keeping the rats at bay. Whenever a monster was foolish enough to cross his threshold, it would immediately be gored with his iron spear. Meanwhile Niner was busy panicking, trying to dig the floor for shards of rock to throw.

“I just wanted to mine iron! What’s so bad about an automaton having a dream?!” He complained.

“Cease complaints and resume ranged support,” Ratslayer scoffed as he thrusted his spear at a large rat.

Things weren’t going well for the three as they were slowly being pushed out of the passage way. If they lose their advantage, they would be overwhelmed. Luckily, they managed to hold on long enough.

‘Drone 8, Niner, Ratslayer, make your way to the outer slime hunting ground. Defense preparations are completed,’ reported Custodian.

The trio didn’t even need to think twice to start dashing towards the outer slime hunting ground. It was a good thing that drones couldn’t get tired, or else they would’ve died from overexhaustion a long time ago.

As the number of slimes they encountered increased, the rat horde continued gaining on them. Slimes were being trampled underfoot by both the drones and rats, who were busy trying not to die or trying to kill.

“Over there!” Drone 8 pointed at a distance.

There was a barricade blocking the entire cavern passage, with six drones manning them. All drones were armed with a spear, ready at a throwing stance. They moved synchronously thanks to the hivespeak, and the fact they could think as one if they enslave their mind fully to an entity, which in this case was Custodian, made them a force to reckon with.

‘Ready, aim… LOOSE!’ Custodian ordered. Spears flew across the cavern, calculated to miss the three drones, but aimed true towards the rats. Rats were impaled as the spears rained upon them. Almost as soon as the first wave of spears were thrown, another round was launched. Custodian didn’t expend or waste a single momentum to increase its killing efficiency.

Meanwhile, the trio jumped over the barricade, then turned to join their brethren. One final spear throw was ordered before the rats clashed against the automaton’s defense. The barricade drones started pushing the horde of rats back, occasionally launching the front plate to knock out enemies which were too unruly.

From above, the drones thrusted their spears down in unison, each time killing a row of unlucky rats. Though the defense was going well, Custodian irked at the fact that some of the barricade drones were being killed. Not only that, some of the original ten drones were being damaged by the rats. Custodian couldn’t afford losing any of the ten drones, as it didn’t know when it would be able to replace them, or if it was even possible to do so.

‘Drone 3, you’ve sustained too much damage, return to the core room for repairs,’ ordered Custodian.

‘Affirmative,’ came the reply.

Things were going so well that Custodian could pull some of the defenders back for repairs until it received a new report.

[Alert: Unidentified organic detected. Barricade Drone 1, Barricade Drone 2, Barricade Drone 3, (...) in danger.]

‘What?’ Custodian examining the battlefield until it saw some odd figures at the back of the rat horde.

Unlike the smaller ones, these rats were bigger, and spikes protruded from the head and limb joints. There were only a few of them, but they pushed through the mob, trying to reach the barricade. Custodian was quickly alarmed by the appearance of the new threat.

‘All drones, retreat into the inner slime hunting ground,’ Custodian commanded.

The original drones were the first to pull back, leaving the barricade drones to hold them off for as long as they could. It didn’t take long for the spiked rats to reach the helpless barricade drones, decimating them.

The plates of bio-iron could only withstand enough force before cracking under pressure, and if the processor was destroyed, the drone was dead for good.

Ratslayer was the last one to pull out of the overrun outer slime hunting ground, swearing revenge for the loss of his smaller kins.

Inside the inner slime hunting ground, small pits were dug and filled with spears. These weren’t meant to halt the advance, only to slow and thin it. The drones, being tall, jumped over the pits casually while the rats chasing them fell onto the death traps, being skewered in the process. Of course, the rats at the back simply used their dead brethren as stepping stone to chase after the drones.

At last, the drones and the rat horde had reached the final line of defense. There were barricade drones, but they had only half the amount of the first line of defense. The drones prepared to fight to defend the core room.

‘This is it. Beyond this is the core room,’ voiced Ratslayer over the hivespeak.

‘Defend the master core!’ All drones echoed their vow in return.

‘All ten of us should be prepared to pull back at any moment, but we must fight for as long as we could,’ Ratslayer continued. He looked at the defenders; some were battered, some had their shields missing.

‘Looks like it’s just us nine,’ thought Ratslayer. ‘Wait… nine?’

“Experimentation is complete. Begin Extermination Protocols. Cry Havoc, and let slip the dogs of war!” Custodian’s deep voice resonated from the core room down the entire cavern passage. The rats froze in fear for a second before returning to swarming the drones.

Ratslayer looked around wondering where the last drone was at until a flicker of a shadowy figure flew passed him. It was just a second, but Ratslayer recognized the figure.

Almost immediately, the ground shook, and rats flew in all direction, some not even in one piece. Another thundering slam was produced, throwing all the weaker rats off the ground. Ratslayer found the source at the middle of the rat horde - A humanoid metallic puppet clad in fur and a set of bio-iron plate armor. Its hands grasped a giant two-handed iron axe, which produced wild lightning.

“Drone 1?” Ratslayer muttered.

Drone 1 didn’t answer as it continued chopping rat after rat without a single shed of mercy - as it could not even register the meaning of it. A red glowing eye gazed at the rats from a slit in the drone’s bucket-like helmet as it judged how it would destroy the most amount of rats with minimum loss of material.

The other nine drones didn’t lolligag as they started their own assault. The barricade drones moved back in order to protect the core entrance, as well as to keep them from being a burden to their older kin.

Ratslayer found the new spiked rats almost as easy as the normal rats, but they still posed a threat with their spikes. They would sometimes curve their body, then spin around to swipe at the drones’ legs, but because they were close to the core room, any seriously damaged drones could simply take refuge there to be repaired.

Drone 8 still had control of the two prototype combat drones, as well as some barricade drones. They were used offensively, trying to crush the rats with the sheer weight of the bio-iron plates, while the combat spider drones were used to strike from the rats’ blind spots.

Eventually, with so many dead, the rats decided it wasn’t worth the trouble fighting the metallic beings. Originally, the monsters wanted to drive them off and kill them, but now, it seemed futile. The spiked rats were the first ones to run, followed by the normal ones.

‘Organics are in full retreat. Do we pursue and exterminate?’ Ratslayer asked.

‘Negative, full extermination of possible material source is counter-productive. I must confirm how they are able to spawn, and if possible, farm them. At the very least, we now know their strength,’ Custodian replied.

‘As you wish,’ Ratslayer obeyed as he and his nine other brethren watched the beasts flee from sight, and into the darkness.

With its job done, Drone 1 rested its great axe against their shoulder, and made their way back to the core room. The rest of the drones followed suit, concluding the first ever big battle Custodian and the automatons had faced, and clearly, it wouldn’t be the last.