Heh. Forgot abt the grey goo
Matter recycling and restructuring.
One of the most useful technologies any space faring civilization can develop is the ability to transform nearly any form of matter into almost any other on the molecular level (atomic would be perfect, but that's a bit more complex and power intensive). The most typical method is swarms of simplistic nanomachines - tell them to disassemble whatever junk you throw their way into convenient high density cylinders for each type of element or alloy found that the more sophisticated (and slower) nanomachines in the printers can then use to make all of the everything else.
Humanity is no exception to this, but they do have their own way of producing some of the more rare types of matter via a little thing they do with their true fusion reactors:
They deliberately overload and blow them up. "Contained" supercharged nuclear explosions using an actual (miniature) star.
"We've got a saying - when you've got a hammer, or in this case - tiny stars - every problem begins to look like a nail that needs an explosion."
Regardless of their insanity, as always, their version of nanomachine reassembly swarms is far more grotesque and dangerous.
For starters, they call them Grey Holes for the simple reason that normally you should not be able to see the nanomachines, as, well, they are on the atomic scale. But not here, no, crank up the density so high that you can see them, and oh yeah, keep them on and active at all times.
Fine, I will be fair and say that Humans do also have normal reassembly chambers that are fully contained, you insert the matter, close the gate, activate the machines, and in a few minutes safely take out the matter cylinders.
What I'm talking about here is a massive, visible, uncontained save for a magnetic field, always active swarm of ravenous nanomachines. They use this Grey Hole, well, okay, that's it's technical name, the workers call it PacMan.
Anyway, they move this PacMan over to a derelict cruiser, a Human cruiser by the way, so when I say massive, I mean it can engulf something that is several kilometers across. In a matter of just a few minutes, they move the PacMan from one end of the gigantic ship to the other. Minutes. Sometimes they play versions of this chipper tune as well. Were it not for the fact a simple electronic pulse even the smallest of ships can generate could fry the tiny brains of these simple machines, no doubt a Dissolution event would have occurred countless times across the Galaxy.
...hmm?
Humans call it the Grey Goo event?
And they knowingly call their reassembly nanomachine swarms Grey Holes. Right. Okay.
sigh Sometimes it feels Humans WANT an apocalypse to happen...