Hedorah is also known as the Smog Monster. It first appeared in Toho’s 1971 film Godzilla vs. Hedorah.
Born of pollution and feeding on pollution,Hedorah is an extraterrestrial kaiju who fell to Earth as a cloud of spores. Upon arriving on our planet,Hedorah hatched into millions of microscopic organisms which began to feed upon the toxins with which humankind has polluted the air and water.
As the tadpole-like microbes increased in number and power, they began to merge into a giant monster of living sludge .Since Hedorah fed on pollution, as long as a small piece of it remained alive, Hedorah could retreat to absorb more pollution in order to regenerate itself.