Hedorah (ヘドラ ) or Hedora, also known as the Smog Monster, is a fictional creature from the 1971 film Godzilla vs. Hedorah (titled Godzilla vs the Smog Monster in the U.S.). The monster was named for ヘドロ (hedoro), the Japanese word for sludge, slime or chemical ooze.
Hedorah was an alien lifeform that landed on Earth and began feeding on pollution. Hedorah's actions soon gained the attention of Godzilla, who attacked the Smog Monster as he was feeding off of a smokestack. At the time, Hedorah was still in a young form, and was easily trounced by Godzilla. The two creatures had a series of battles across Japan, and Hedorah continued to grow bigger and stronger, and achieved a flying saucer-like form, allowing him to fly and spread sulfuric acid mist across Japan. Hedorah and Godzilla had a final showdown near Mt. Fuji, in which Hedorah achieved his final form, a humanoid, walking pile of sludge. Thanks to his acidic, poisonous body, as well as his lethal eye bolts, Hedorah very nearly put an end to Godzilla in their struggle. However, mankind had built a pair of gigantic electrodes near the warring kaiju. Their plan was that, since Hedorah was merely sludge, they would use the electrodes to dry him out. During a period of the fight where Godzilla was knocked out, Hedorah was lured between the electrodes. Unfortunately, a fuse was blown, and the electrodes were useless.
Thankfully, Godzilla quickly came to the rescue again, using his ray to re-energize the electrodes. Badly dehydrated by their electricity, Hedorah tried to escape, but thanks to Godzilla's newfound power of flight, was returned to the electrodes and was dried out completely. Sensing that there was still wet sludge within Hedorah's dried out husk, Godzilla proceeded to rip out Hedorah's innards, then used the electrodes to fry them. Godzilla had finally slain the hellacious Smog Monster, but not without a price - he had lost one of his eyes, and his right hand was burnt down to the bone.
Hedorah later returned, albeit briefly, in Godzilla: Final Wars (2004). Hedorah, along with Ebirah, is seen being blasted out of Tokyo Harbor by Godzilla and crashing into a building, with Ebirah's claw piercing Hedorah's eyes. The two are then destroyed by a blast of Godzilla's atomic ray. It is unknown if Hedorah had been involved in the Xilians' invasion, or if he was simply in the wrong place at the wrong time.During the end credits a few deleted scenes were shown, one of which was Hedorah using his sulfuric acid mist emitted from his body tube (see right for example) while walking down a deserted, destroyed city.
Hedorah may or may not be the monster from Godzilla 3D to the MAX. The creature who is to appear in the short, 40 minute film is called Deathla. While it looks like Hedorah, it feeds on chlorophyll (not smog) and can split up into a swarm of locusts, and reassemble at its own will.