The compound at the center of the reputation is tetrodotoxin. It also occurs in pufferfish, in some newts, and in some frogs. What is unusual here is the delivery. The blue-ringed octopus is the case in which this toxin is used as a venom, injected, rather than only as a poison sitting in flesh that something might eat. Chemists first knew the octopus compound as maculotoxin. In 1978 that name was retired into tetrodotoxin.
Tetrodotoxin blocks sodium channels on nerve and muscle. Signals that depend on those channels stop. The effect that matters most, in a person, is paralysis, including the muscles that breathe. Death, when it happens, is usually suffocation because the diaphragm has stopped, not a dramatic failure of the blood itself. People who have been badly envenomed are often awake. They can hear. They cannot move, and they cannot ask for help. The comparison often drawn is to drugs like curare, which also leave the mind intact behind a body that will not answer.
The venom is not tetrodotoxin alone. Histamine, tryptamine, octopamine, taurine, acetylcholine, and dopamine have all been reported in the mix. The sodium-channel blocker is the piece that makes the paralysis famous. The rest of the cocktail is part of why a bite is a medical event and not a clean textbook diagram.
There is no special courage, and no special meal, that makes this interesting to test. The same molecule is why pufferfish chefs train for years, and even then the tradition is a risk people argue about. An octopus in a pool is not offering a lesson you can learn with your hands. This journal will say what the toxin does. It will not say how to extract it, how much is in a gland, or how to handle the animal “carefully.” Carefully, here, means not at all.