The four decapods halted their plunge. Above, the craft split into pieces and left another wired object on the underside of the ice. After separating, the craft resumed the descent, pinging sporadically. The four decapods continued to fall with it, pinging back and projecting the idealized image of Deepvent. They slimmed or expanded their body’s skin as needed to keep a constant distance in front of the alien object.

The cool water and the lack of food had made them ravenous, and they snacked on their ration of krill. The trip was simple—they only needed to drop like a rock, and the stone was doing all the work. One decapod stayed awake while the others dozed with happy stomachs.

It was difficult to slip into torpor. Each hope was high and thoughts were booming. So bright were their expressions on everyone's skin. They all could read their minds. With the rock, pictures, Study-Up's food research, the theory, and of course The Loud Metal Thing, they would finally prove to all that another world existed outside the ice.

The fact the metal probe had communicated ‘hydrothermal vent, baleen shark song’ was exciting! They could see the sono-pictorial images and count the pings, but everything else was undecipherable. Though they theorized The Great Attractor was could be made of metal, sand, or foul water, the fact this extra-planetary descender played underwater sounds over and over gave them hope there was another ocean planet not far away. Ice-Driller thought. It must be very close indeed, since this was obviously a machine. He continued to speculate about the distance. Sure, sound must travel differently through the void than through water, but if one halves the time, then it was something like 1/15th of a sleep cycle away. Okay, stupid thoughts, no one can swim as fast as sound can carry. It has to be at least one hundred times as far away. Ice-Driller thought.

Optimism was flowing into his tentacles, and he was happily leading the odd caravan back to Deepvent. He tapped on his friends with a dot-rub-dot; which was a simple message of happy physical communication.

Proof of other worlds to inhabit, and other intelligences to learn from should—no must—diffuse tensions.

They continued the rapid descent. Occasionally, one of them would ping backwards at the machine to make sure it was following them. They would shoot a cone of sound towards it—images of a hydrothermal vent—and like clockwork, the object would ping back. And so The Overworld-Object continued to follow them. If it started lagging, then one decapod would increase drag and slow down their bottomless descent.

Finally, they neared halfway. They knew from the pressure, but also the scent of jellies in the black water. And where there is prey, there are predators.

“I taste something in the water.” Study-Up said.

“Slow up,” Ice-driller said. They all deformed their bodies to take up more cross-section and changed their speed.

“I smell it too,” said Sand-Stirrer.

“We may need to punch through quickly if we hear a mandible shark.”

Sounds were coming from below. Big sounds. The kinds of deep sounds that occur around the die-cast foundry or other heavy industry such as rock moving. As they drove down, the machine behind them sent out another loud ping.

“Ough, Thing, stop—” said Sand-Stirrer.

A returning echo hit them back. They visualized the many huge objects below them.

“Sharks!” Sand-Stirrer said.

“Impossible—a floating town?”

Silence! Ice-Driller tapped out to each of them. They streamlined their bodies for a fast descent. The visual from below was of many large fins, but not sharks. They were baleen-fins towing platforms with repetitive stacks of dense materials. They all tensed up with terror. Involuntary red streak of fears came over their otherwise hueless skin. They maintained silence and could not communicate with the machine.

Another from above.

The scene below was lit plainly.

The war had started.

Ice-Driller tried to tap out what he saw, but the tap language was too slow and cumbersome for the topic. This was an artillery position, dropping rocks onto the city below.

Oversea bombardment.

This platform was so high to discourage any counter-attack. The time for which city defenders would need to swim up, fight the platform, and then swim back would weaken a cities’ defenders more than enduring bombardment.

Offensively, if a rock hit a fort and destroyed it, it was a formidable boost to the attackers—pinned decapods were easy to kill. If the rock missed, it was just a rock, and nothing was lost but the energy and time to haul it up. The secondary psychological effects were also there. Raining death kept decapods under cover.

The platform had a unit of ten guards spread around the outskirts of the platforms. Previously, they had floated idly around, protecting the platform from any potential attack. It was a choice assignment, away from the fighting, and few predators to chase away.

The ping from the machine startled the defenders into action.

The siege engineers, about twenty, also stopped their bombardments and looked up, terrified they had been outflanked from above.

Their strange dialect confirmed the worst in Ice-Driller's mind: the army of Hotsmoke was below. “Dive fast!” he said.

The four decapods all pulled in their bodies into a streamlined shape and they dove even quicker—too fast for any reaction from the guards. By the time their echolocation pings returned to them, the quartet had almost passed through their positions.

“Bye.” Thermal-Rock taunted.

The following machine threw out more loud pings as it encountered the scene, which confused the besiegers as they visualized more echoes above. Panic almost set in, as a few soldiers went full arms out and instinctively darted away from the noise. After the spurt of panic, cries of cohesion rang out.

“Hold position!” A sensible lieutenant cried out. Then other calls swirled around as the four decapods approached the middle of their formation.

One brave defender swam towards the four.“Get the ADDMs” One of the enemy siege operators said.

“Too close,” replied another. General disorder ensued as they switched to anti-decapod dart munitions instead of dropping the large inert rocks they had previously dropped.

The attacking army had large canisters filled with long thin flechettes that might only maim a decapod if it hit an arm, but could also pin it down. A direct hit on a creature in the open would certainly kill it, but with multiple hearts, arms, and neural nodules, the decapod could often survive. But the edge of the darts contained small grooves that sped up blood loss. The ammunition's delivery sabot was set to release the darts at a specific depth to prevent the currents from carrying the submunition too far. The four diving decapods were too close, and the gravity of their planet was too weak to do damage at close range.The one pursing defender threw a harpoon that missed and fell into the depths.

Down the four decapods went and The Object still followed them.

“The war’s started!” Ice-Driller exclaimed.

“Let’s see if we can end this madness.” Replied Study-Up.

Two canisters of anti-decopod munitions were readied, but the captain thought it was senseless to do any more and called to his troops to resume the rock bombardment. The coarse raw rocks were slow and not designed for a kinetic kill. Instead, they were used to crush normal buildings, which were often little stronger than a clamshell. Since these rocks took no effort to produce, (only hauling them to position) they made up a majority of the ammunition used.

The siege platform also had bunker-busters. These were shaped metal ores with a simple gas emitter at the bottom tip, which allowed the munition to ride on a bubble of air down. This increased their speed and precision. Combined with knowledge of the currents, attackers could accurately hit a building from great heights. The supercavitating ammunition could crack open even the strongest of domed defenses.

“Throw out sand.” The captain cried. This was the last sound that any of them could make out as they continued their fast dive towards home.

Another tool in the sieger’s arsenal was large bags of silt sorted by particle size. The fine particles could be used defensively to cover an escape if the besiegers were attacked, othertimes sand was placed in canisters that would explode over the defensive position. They often used these during the last assault to hide the attacker’s approach and dampen the defenders’ coordination.

“They’re already attacking Deepvent? So soon?” Study-Up asked.

“Plans must have already been in motion.” Ice-Driller said. “All we can do now is diffuse the result.” Quivers of fear ran through the closely bundled group. Ice-Driller then tapped out a message with his tentacles to his three crew:, , .

Above them, The Object continued to descend quickly with the decapods. It continued to follow the phantom-emitting crew of Ice-Driller, who all took turns continuing to send the sono-pictorial image towards the craft. The echoes from above them returned nothing from the wall of silt above that was descending slowly.

“What if they drop darts at us?” Thermal-Rock asked.

“Still too close for lethal damage,” Sand-Stirrer said.

Downward the quartet of decapod discovers continued to fall through the long, dark, cool water. Behind them, the strange object followed unwaveringly.

“How far?”

“Feels like we’re getting close.”

They could tell by their subtle changes in physiology and the way the sound sounded. Other sense piqued. Soon, then picked up a fresh scent of old blood—the whiff of copper in the water far off.

###

The probe descended through the nearly empty, lifeless wastes. Scientific instruments were brought online. Sensitive mass spectrometers and other instruments detected more signals of life. It sensed the copperphyllic protein, haemocyanin, which was not alien to Earth and occurred in earth-animals optimized for the cold water. It tagged and logged the odd collection of data it had just encountered, but the probe's AI was unmoved. Earth's marine biologists estimated that mid-column life was too scarce, so the probe did what it was programmed: pursue the highest rated scientific goals.

The navigation AI rightly concluded it was not a seamount, (though there were often disagreements in the exogeology community about how large a mountain could exist on a lower-gravity world). Sonar continued to be emitted, and the same image continued to return, a small something in the distance that emitted curious signals akin to its highest priority. So the probe followed.

Another scientific goal was the cataloging of oxygen levels along the entire depth of Europa. The tidal flexing of the moon as it moved around Jupiter caused vertical currents. Scientists had estimated currents alone oxygenated the entire ocean, but now the probe was collecting hard data. The oxygen itself was created through the interaction between Jupiter’s radiation, striking the H2O molecules, freeing the hydrogen to float out into space, but trapping the oxygen to allow complex life on Europa. This was a non recyclable process, in sharp contrast to Earth’s. Eventually all Europan life would suffocate, but over a timescale of billions of years, in the same order of magnitude as Earth's eventual fate. Still, this was only theorized and calculated, and backed up some by the Europa Clipper's analysis of plume sprays, but the theory's eventual fate rested in the data collected by the probe.

Though protected due to distance, the far future fate of Europa was under-theorized. Whereas the expiration of Earth because of the swelling of the Sun into a red giant had been known and communicated for decades on Earth, it was unknown whether some future process might reoxygenize Europa.

###

The dull sound of fast descent dominated the decapod audiovisual senses, but slowly muffles from the deep climbed up into their audible range.

“Do you hear something?”

They all popped their heads back and forth to detect the sound. It was the wail of distant alarms.