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.
- 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?