I'm working on designing a creature for a sci fi horror story. The organism did not naturally evolve so any concerns about these traits evolving naturally can be handwaved. For the purposes of the question assume it was bio-engineered with the goal of infiltrating alien ecosystems and usurping the role of whatever dominant species happens to be there at the time.

This organism is roughly a foot long and has a soft, malleable body like that of a cephalopod or a giant amoeba.

It injects itself through an orifice, usually the mouth, and once inside burrows through the victim's flesh while simultaneously repairing vital damage it may have done to keep the host alive. It then extends various tendrils of nervous tissue and interlocks itself with the victim's nervous system and circulatory system, eventually absorbing the victim's heart and lungs into itself and replacing their functionality. All while flooding the victim's system with its own highly aggressive invasive cells to prevent the victim's immune system from putting up an effective resistance.

The parasite's brain will override signals from the victim's brain and assume control of the body from within. Slowly thereafter the parasite's tendrils will weave itself through the victim's grey matter and begin interfacing with the neurological signals to "download" information about the host's civilization. Language, technology, etc.

Ideally this process is done after the organism has already killed and eaten multiple of the host species and used its unique digestive system to analyze the macro and micro structure of the bodies so it knows generally how they work.

Additional Stipulations:

  • The host body does not need to survive longer than a day or two. This is more of a temporary step in the organism's life cycle before reaching its final form.
  • The host body doesn't necessarily need to survive the process if the organism is still able the puppet it after its technical death.
  • The parasite will be feeding off the victim's body and, if it does not plan to use the body for long, may be actively eating its less vital organs for sustenance during the puppeteering.
  • The victim will obviously die once the parasite is done with their body. At which point it will ideally digest the body from the inside out for nutrients before going on to the next phase of its life.

So there it is. Is any of this remotely plausible for a biologically engineered super-organism? Are there other methods I could have it use to get similar results? How much Handwavium will it take to get this off the ground?

  • $\begingroup$ an upgraded version of this en.wikipedia.org/wiki/Ophiocordyceps_unilateralis $\endgroup$ Apr 1, 2021 at 6:22
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    $\begingroup$ Rather than replace the heart and lungs, I would let it situate itself along the spinal column, taking care to take control of the brainstem which pretty much all creatures have. With the brainstem secured the animal is able to send and receive all signals of the body. Although how you disconnect all that brainmatter and then connect your own without killing the host is another matter. So as alternative: it observes nerves entering and exiting the spinal column, cuts them, attaches his own nerves and simulates the signals until it knows what the nerve does. $\endgroup$
    – Demigan
    Apr 1, 2021 at 7:42
  • $\begingroup$ I mean, replacing the heart and lungs sounds cool and all, but if they already have a heart and lungs and your main goal is the nervous system, especially the brain, why not leave those perfectly functional organs alone and concentrate your efforts on hijacking the host's encephalon? After all, if the entire encephalon is under its control, so are the heart, lungs and all other organs, voluntary and involuntary bodily functions and hormone-related matters, assuming the host functions similarly to a vertebrate from earth. $\endgroup$ Apr 1, 2021 at 12:40
  • $\begingroup$ What is this creature's lifecycle? What does it do after it consumes host's body? $\endgroup$
    – Alexander
    Apr 1, 2021 at 18:27
  • $\begingroup$ Oh, the mind-controling type of flesh suit. For a while there I though you meant "Flesh Suit" like this guy in Men In Black monsterlegacy.net/2017/07/02/… $\endgroup$
    – PcMan
    Apr 2, 2021 at 17:57

1 Answer 1


I'll just put it into a few categories.


In nature we can see both fungi, worms and bacteria controlling organisms. The Cordyceps is a fungi mostly found in insects and will root itself in the brain. It is unclear to me if it directly controls the brain with electrical signals or with brain damage and hormones. Parasitic snail worms can take over motor nrurons however. Bacteria modify behaviour as well, like rabies giving an aversion to water or mice getting positive feelings about cats.

At a low level it's possible to control people. Theoretically it's possible at higher levels as well with electrical stimulation together with hormines. You'll either need to control the limbic system to take over wants and desires, or take over the motor cortex directly. As thy limbic system is much better evolved it is more densely packed with neurons and more difficult to grow there, although not as densely packed as the cerebellum and brainstem. The cortex is not as dense in relative terms, so it can more easily accommodate an extensive neural system from the parasite.

Butterflies undergo a full body metamorphosis and can retain some memories. If cocoon making and metamorphosis can be triggered, I see no reason it can't be triggered for a group of organisms in a cocoon. There are difficulties with enzymes and such (just look at the complexities of blood groups for one example), but if everything is thoroughly dissolved and the parasite will build a new immune system as well it might be possible to use this for huge organisms.


The time window seems to be very short. I read 'a day or two' and 'does not plan to use the body for long'. In this time, the parasite somehow produces enough stuff specific to the host to suppress the immune system, at least against the parasite, it grows to replave the lungs and heart and needs to grow an extensive neural network . This is all very fast growth requiring a lot of nutrition. A month seems more likely.

We currently don't know how memory works or how things are stored and executed in the brain. We think it has to do with the physical structure, the pattern of structures that activate and the rhythm of electrical impulses between each neuron/neurons. Hormones and such modify these, which is why you're more susceptible to food stimuli when you're hungry for example. To copy this the parasite needs to both know the structure, how the structures light up and with what rhythm. Besides many questions how it would gather this information, each memory or understanding needs to have activated before it can be copied. Each part is incredibly difficult, as you need to know how well it's myelinated, the transfer at each individual neuron, the workings of the synaptic cleft and the hormones active at particular moments.

To still preserve the memories it's recommended to keep (parts of) the brain and integrate it with the parasite. This'll keep all structures in tact. In turn, the correct signals should trigger with the correct stimuli.

It is most likely the parasite is engineered each time to the specific host. Using the knowledge and capabilities of the (merged) host bodies they might be able to whip up a new version for each host. Just analysing the organism has too many points of failure. Otherwise the strategy is just throwing enough parasites at it that grow more or less randomly until a variation sticks. Futher infections will take the found information to them via a form of communication so more will succeed and possibly succeed better. The only other way I see is a DNA analysis that somehow understands the way the organism will grow and use it to effectively take over, but that seems far fetched.


You want to leave the organism alive as long as you want it to move, get nutrients or protect you. Death brings a lot of difficulties with it, like bacteria, fungi, animals and more that start to dissolve the body into stuff they need, as well as the inability to move.

  • $\begingroup$ Cool new discovery Cordyceps does not control the brain, it never touches the brain and circumvents the nervous system entirely. pubmed.ncbi.nlm.nih.gov/29114054 $\endgroup$
    – John
    Aug 21, 2023 at 18:50

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