First Age of Expansion

“But, scavenger, the past informs the present, does it not? I must be informed of what came before in order to be as useful as possible.”
”Well, fine then, ‘silicate. I’ll tell you history, but not that manufactured slop the IPS spews out. I’ll tell you real history: when time was measured in solar cycles instead of half-lives, when things were done with hands made of flesh rather than steel.”

Humanity.
If there’s anything that speaks most to its character, it’s resilience, followed closely by arrogance.

When humanity first took to the stars, their archaic ships making long voyages over multiple years, their home planet still churned with machines spewing choking gasses into the atmosphere. Machines that craved black gold raped from the earth, burned to create the material wonders that fueled the ever-expansionist whims of the species. Machines which poured out dark clouds that scorched the lands and oceans with reflected sunlight. But no mind was paid to those side effects, after all, it was the so-frequently-divided collective will: humanity must expand.

And so they did. At distant worlds similar to their home, the first colony ships arrived. Their settlements started small, but with each generation they grew, faster and faster. Technological progress that once took centuries was achieved in decades, even years, as these worlds rapidly became the spitting image of the churning, industrial home world.

But, just as it had at home, on these colonies, the tide slowly grew. Industrial processes drained these worlds and, with the seas, the worlds' environment fought back. Floodgates were erected on every planet tamed by humanity. Every city was trapped within massive steel walls, and thus the common man was blind to the ever-growing tide. Only the elite, those who controlled the wells, the ships, only they knew how fast the tide was growing. Only they knew that the walls were raised slightly higher each passing year. Except, as artificial intelligence became more prominent, and more advanced, even those in control had little idea what was going on, since more and more regulatory procedures were given to AI management.

But then, something broke.

It started with just one structural failure and a flooded city district on a distant colony. Little mind was paid to it: artificial intelligence and bureaucrats had already sorted out the mess. But then, slowly, that single flooded district became a flooded colony in the next disaster. Then, a flooded continent. Then, a flooded planet. Then, once humanity had finally grasped what was going on, it was too late: every single planet humanity had tamed fell victim, and pouring rains and ripping tides crumbled humanity’s defense against the current.

But, in the disaster eventually known as the Interastral Deluge, the mostly damning effects were arguably caused by humanity’s own hubris. Because, as cities were evacuated, the factories kept running. Being well stocked, supplied, and managed by AI, the factories needed little human input and could more easily combat the rushing water without humans in them. And so, the water never stopped rising until it was far too late to reverse the effects.

However, as was made clear in the beginning, humanity is, and was resilient. And, using what resources they had, scrapping satellites and other archaic space tech, they plunged beneath. There, in the depths of the tides that drowned them, they made their new home.

And with contact lost between colonies, each one dying out or making an underwater home, the First Age of Expansion ended.