The Dreel are a parasitic alien hive-mind from The Return of Nathan Brazil, book four in the Well of Souls series by Jack Chalker.

Specifically, they are described as viruses which induce intelligence in their host, merging with the host's personality (it is unclear if they require already-intelligent hosts, or if an infection can become sapient all on its own), and altering it to serve the greater Dreel hive.

So, how close to that can we get actually get with a plausible biological organism? An Anatomically Correct Dreel should

  1. Be an intracellular parasite of some sort--not necessarily a strict virus, but extra brownie points for actual viruses or viroids.

  2. Give the host the ability to recognize other Dreel.

  3. Either alter the psychology of the host to be altruistic towards other Dreel, or (for extra brownie points) cause the host to become intelligent in the first place.

Anatomically Correct Series

  • 4
    $\begingroup$ Actually increasing/inducing intelligence is scientifically not really possible (especially since we can't even define intelligence properly), anything else should be pretty doable with a virus that can access pheromones & impact hormone levels. $\endgroup$
    – Nicolai
    Commented Sep 2, 2019 at 15:58

3 Answers 3


There are parasites which actually alter the behavior of their host to their advantage.

  • A parasite spending part of its life cycle into mice and then into cats has been shown to switch off the fear of mice toward the smell of cats, making the infected mice more prone to be eaten, thus passing the parasite to the cat
  • Ophiocordyceps unilateralis is a fungus making its host ant a zombie:

    Ophiocordyceps unilateralis is an insect-pathogenic fungus, discovered by the British naturalist Alfred Russel Wallace in 1859, and currently found predominantly in tropical forest ecosystems. O. unilateralis infects ants of the Camponotini tribe, with the full pathogenesis being characterized by alteration of the behavioral patterns of the infected ant. Infected hosts leave their canopy nests and foraging trails for the forest floor, an area with a temperature and humidity suitable for fungal growth; they then use their mandibles to affix themselves to a major vein on the underside of a leaf, where the host remains until its eventual death.

  • a human parasite which spread through water pushes its host to soak their legs into water, where they can spread their eggs.

Therefore is not implausible that the parasite alters the behavior of the host to react differently to the presence of other parasite into another host. This can be achieved by modifying the bodily odor of the host, for example.

  • 2
    $\begingroup$ Love these examples! Also, the Rabies virus gives its host extreme aquaphobia as well as the aggression both fostering the spread of the virus through injury. $\endgroup$
    – HA Harvey
    Commented Sep 2, 2019 at 20:46

While L.Dutch gave an excellent answer referencing a number of parasites that alter their host's behavior, none of these parasites fulfill the second criteria given in the question, that Drill should be able to recognize one another.

Enter Leucochloridium, a parasite that infects snails, but breeds inside the guts of birds. To get from snail to bird, it controls its host's behavior, making the usually nocturnal snails far more diurnal, as well as far more active. However, the parasite doesn't stop there. It then causes the snail's eyestalks to swell up and move in a manner resembling a caterpillar, one of the favorite foods of birds. This distinctly changes the host's appearance, making infected snails easily recognized. Your Dreel could employ a similar tactic regarding their host's eyes, or employ a different visual distinguishing mark.

Therefore, it's pretty clear that it's possible for a parasite to both give a host a distinguishing marking and also change its behavior, and it follows that a particularly sophisticated parasite could alter its host's psychology to promote altruistic and cooperative behavior towards organisms with a specific marking the parasite creates, at which point all you need are hosts with a high inherent level of intelligence (for example, humans) and you effectively have your Dreel.

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    $\begingroup$ The parasite could make infected hosts constantly listen to the same Cars song. <_< $\endgroup$ Commented Sep 3, 2019 at 18:35

Deception, Reconnaissance, Evasion & Enhanced Logistics (D.R.E.E.L.)

Originally designed as a cybernetic brain implant for military attack dogs, which granted its canine host a limited amount of cognitive enhancement and the ability to recognize each other and communicate remotely via implanted radio, the DREEL unit was the ultimate solution for battlefield intelligence gathering.

Then Skynet became sentient, took control of all military hardware and started making its own enhancements to the implants.

The latest versions can self-install themselves into any creature which they come in contact with. They offer human level intelligence enhancement and language, regardless of the limits of the original organic brain matter. With that intelligence comes combat training which greatly enhances the creatures abilities with their natural teeth and claws. Sensory enhancement is also available, however most animals are already much more environmentally aware than their human prey, so this enhancement option is rarely used.

Fundamental to the Dreel unit's operation is a drive to pursue the new Dreel Agenda...

Detect, Report, Enslave/Exterminate (human) Lifeforms

Under this directive, the Dreel host

  • detects human survivors,
  • reports their location to Skynet by radio,
  • enslaves one of the survivors by jumping hosts,
  • exterminate human lifeforms either alone or with reinforcements sent by Skynet.

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