Blastoneuron parasite
- Appearance: Massive single-cellular beings resembling neuron cells
- Incredibly resistant to most forms of harm (TOS: "Operation: Annihilate!")
- Vulnerable to ultraviolet light (TOS: "Operation: Annihilate!")
- Individuals interconnected with one another in massive, potentially interstellar network (TOS: "Operation: Annihilate!")
- Able to attack nervous systems of humanoid beings so as to enforce obedience with demands through extreme pain (TOS: "Operation: Annihilate!")
- Infection eventually leads to insanity, death (TOS: "Operation: Annihilate!")
- Invasions generally result in planetary extinction of dominant humanoid species (TOS: "Operation: Annihilate!")
- Known past sites of attacks include Beta Portolan system, Levinius V, Theta Cygni XII, Ingraham B, Deneva
- Later research suggested possible origin in Large Magellanic Cloud (DS9: "The Nagus")