Hedorah was named for hedoro, the Japanese word for mud. This is especially befitting, due to most of Hedorah's attacks involving releasing acid-rich dirt at his opponent.
In its first form, it resembled a tadpole. In its second form, it resembled a quadrupedal reptile. Its third form was like a flying saucer, and its final form took on a humanoid shape.
HistoryDark Gas Nebula, landed on Earth 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 while destroying many factories. 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 monster. 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 new-found 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 killed Hedorah, but not without a price; he had lost one of his eyes, and his right hand was burnt down to the bone. At the end of the movie, a picture of another Hedorah is seen in some water, with the caption 'And yet another one?', but no sequel to the film was produced.
The Hedorah in Godzilla vs. Hedorah killed thousands of people. Hedorah killed some of the oil tankers' crew mates, most of the swimmers and fish in the sea, about 40 people on the first time he went on land, 1600 people when it was first flying, an unknown number when he was flying to Mount Fuji and about 80 of the people who were partying on Mt. Fuji. Also, over 3,000,000 people were affected by Hedorah's smog. Strangely enough, it is not shown in the Millennium series whether Hedorah kills any people at all.Godzilla Island.
There was also another Hedorah in Godzilla Island called Neo Hedorah.
Hedorah is one of the strongest opponents Godzilla faced in the Showa series (though Godzilla easily defeated Hedorah in Final Wars, which means that either the Millennium Hedorah is much weaker than the Showa, or that the Final Wars Godzilla is far more powerful than the Showa one). Hedorah possessed many special abilities. Hedorah's primary form of attack was by squirting chunks of its own acidic body at its opponent, as well as a red laser beam from its eye. In its saucer form, it was also able to fly, and spread a mist of sulfuric acid as it went along, and in its final form it could revert back to its flying form at will. Hedorah can reproduce asexually, can combine with and separate from other species, and does not need oxygen to survive.
Hedorah is shown to also be able to release massive quantities of sludge and dirt without this affecting his size in any way, as shown in Godzilla vs. Hedorah where he traps Godzilla in a pit and releases so much sludge into the pit that it nearly covers Godzilla.
Hedorah has strong defenses, as it was completely immune to Godzilla's atomic breath even in its comparatively weak second stage, and conventional weapons would merely pass straight through its disgusting body. Tearing into Hedorah's body proved to be ineffective as well, and it resulted in the flesh on Godzilla's hand dissolving all the way down to the bone, as Hedorah's blood alone is very toxic. Only his eyes are known to be affected by his own liquid sludge, and when he bleeds over one of his eyes, he has to shut the eyes to prevent it from being damaged. In the ending credits of Godzilla: Final Wars, Hedorah is shown spraying sulfuric acid mist from tubes on his body, while stomping through city ruins. In Final Wars, Hedorah was also given a whip-like arm, which he may or may not use in battle.
Hedorah appears as a villain in the 1988 Nintendo game Godzilla Monster of Monsters, as well as the sequel, Godzilla 2: War of the Monsters. Hedorah was an enemy in Gojira-Kun and the Godzilla Gameboy game as well, and was unique because Godzilla's blows couldn't hurt him, but rather push him back somewhat.
Hedorah also makes an appearance in Godzilla: Destroy All Monsters Melee, where it randomly appears in disc form and slows the energy recovery. It can be killed, though this is difficult. When it is killed, it turns into a puff of smoke which dies away.
Hedorah was stated to appear in both of the Godzilla: Destroy All Monsters Melee sequels but for Godzilla: Save the Earth, the game's engine couldn't develop a skeleton for Hedorah since it is a gelatinous blob, and for Godzilla: Unleashed, the cel-shading was a long and complicated process so Pipeworks decided to scrap him. Since Battra's appearance in the PlayStation 2 version of Godzilla: Unleashed, Hedorah has become the most wanted playable monster for a video game.
Hedorah is featured in the fourth issue of the miniseries Godzilla: Legends. In this issue, MechaGodzilla is sent to China in pursuit of Godzilla. Once the mech and its crew arrive, they find that the entire area has been destroyed and that the air is full of toxic mist. The source of the devastation is revealed to be Hedorah, who attacks and overwhelms MechaGodzilla. Before Hedorah can destroy MechaGodzilla, Godzilla himself arrives and reluctantly joins forces with his mechanical double against Hedorah. Hedorah puts up a savage fight against the two monsters, but in the end is defeated by their combined might.
In Godzilla: Ongoing, Hedorah is one of the space monsters that attacks Earth, the others being Gigan, SpaceGodzilla, and Monster X. Hedorah does battle with Kiryu and almost destroys him, but Godzilla arrives and takes on the smog monster while Kiryu escapes to get backup. Hedorah badly wounds Godzilla with his deadly toxic body and knocks him into a canyon, where he attempts to drown Godzilla in toxic sludge. Godzilla uses his atomic breath to fly out of the canyon and resumes his battle with Hedorah. Godzilla tears Hedorah into pieces and burns him into dust with his atomic breath. Godzilla then leaves to battle the other space monsters, leaving Hedorah apparently destroyed.
Hedorah appears in The Half Century War #3 as one of the many monsters battling in Ghana in 1975.Godzilla: Rulers of Earth, as part of Dr. Kenji Ando's conference about the reasons why kaiju have gained their own place in the natural order. In the presentation, it's learned that the "Smog Monster," as the news like to call Hedorah, attacked several oil rigs in the ocean.
Hedorah's gurgling roar comes from Kemular, a poison gas monster the original Ultraman series.
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