Black hole? Feed them materials until they grow into range of a star’s gravitational pull, pulling all of them and burning them? Ramming them with the hyperspace shield?
"Plot armor saves the day." Jk. It seems like your protagonist will go through hell, or something like it. I feel sorry for him/her/other.
They don't inherit their ferromagnetism at least. If they absorb iron, they will be more conductive compared to if they absorb titanium, but they won't be magnetic as the materials do not exist in its metallic form, but only as its elements, ferum.
Before they can grow into that mass though, they would've split themselves into children forms. So feeding them only makes them more dangerous.
Another possible solution depending on mechanics of the novel. Using: Gravity against it. Or maybe taking the ship close to light speed. Even a piece of grain could vaporize the ship. Flood the ship with plasma. Nanobots. Kill them before they board the spaceship. Sonic weapons. Radiation. Shields. Lasers for cauterizing.
salt lots and lots of salt, rusting them from the outside and even if they absorb it would still destroy them, a living being can only take so much salt more so if they have metal in them
Suicide bomb drones. You effectively take advantage of their desire to latch on to reproduce and blow them up sky high.
It's only metal. Most metals melt by 2000C. IIRC, none stay solid beyond 3000C. In fact, most metals and materials vapourize by 2500C. So your classic nuke is more than sufficient to do the job. Fusion bombs will be more efficient, anti-matter bombs even more so. So, to be safe, you nuke their engines. Then you bomb them like those old stories where you bomb asteroids to redirect their course away from Earth. Except in this case, you direct them to the nearest star.
hmmm... what level of technology would one have access to deal with them? Imaginary weapons (weapons that cause a singularity/black hole for a short period of time) sound like they would make a short job of them Spoiler: Example, contains spoilers of I reincarnated as a genius The weapon used by the MC to kill the zombies there is a perfect example here Plasma Weapons sound viable, Lasers too, luring them near a black hole and then firing stuff with enough force to push them towards it's gravitational field sounds good too
Elemental iron, potential for oxidation reaction? Perhaps create some reactive oxygen species to cause free radical damage? I mean we're talking on a large scale here, but they must have some cellular/DNA component? Kill the brain?
Don't know how to describe the level of technology. Ai-chan doesn't think Kardashev scale applies here. The protagonist's ship has a beam weapon that is described as 'hadron beam' which shoots subparticles at the target which also affects subspace. This is a plot device to be used much later, against a great horror that live partially in subspace. Their technology are not really theirs, but granted by a much more advanced being who once helped humanity's ancestors escape that great horror 100,000 years ago. In this story, humanity's original homeworld Edea was overrun by the great horror 100,000 years ago and had to escape through a stargate to Earth following an invitation from a reptilian race.
From what I gather, they need physical contact with physical matter to reproduce. Ie. lasers, phasers, plasma etc. should work well against them if powerful enough. Black holes / antimatter or the equivalents would probably solve the problem as well. So, set up a few black holes in a region / lure them to such a region / prepare antimatter weapons. Use lasers / phasers / plasma with knockback effects to force them into the holes / into a more confined space for better effect. Antimatter / blackhole the hell out of them
Plasma Cannon seem good choice for this one or distruptor also good because it's damage molecular bounds. Exotic weapon also good maybe for example void type weapon, they harness energy causing ship change into dead metal by using entropy but ineffective on metal. Also I remember lots of it on novel or manga that seem effective let's make a list then: Thanathonium: space denotation type( I forget the manga name) Matter descontructor: ender game Graviton cannon : highly consecrated gravity on tight beam Viper : space displacement Antimatter weapon: you know top tech tree weapon Well there is lot other too
NAKAMA on a serious note: What is the amoeba civilization like? Is it a hive mind or just a really aggressive mold? If the ship maintains its metallic properties it would be possible to create a magnet powerful enough to tow the ship into a gravity well. Using physical shells or rockets wouldn't work since the mold will just add it to their ship, so they protagonists would need to use energy weapons like electricity or heat beam
It's a very aggressive mold. It's not a hive mind. They are not neurally connected. They're like single-celled organisms that just so happens to grow next to each other and move together following a common instinct. They don't have the kind of brain that we associate with multi-cell organisms. Only once a critical mass is reached that the blob of stuff split into children forms.