It is an amatoxin, a group of toxins isolated from and found in several members of the Amanita genus of mushrooms, one being the Death cap (Amanita phalloides) as well as the Destroying angel, a complex of similar species, principally A. virosa and A. bisporigera.
Amanita | Amanita muscaria | Amanita phalloides | Amanita Design | Amanita nothofagi | Amanita bisporigera | Amanita australis | Amanita strobiliformis | Amanita Pestilens | ''Amanita muscaria | Amanita caesarea | A collection of ''Amanita ceciliae'' showing typical colouration, from Piacenza |