In Norse mythology, Níðhögg or Níðhöggr is a dragon/serpent who gnaws at a root of the world tree, Yggdrasil. In historical Viking society, níð was a term for a social stigma implying the loss of honor and the status of a villain. Thus, its name might refer to its role as a horrific monster in its action of chewing the corpses of the inhabitants of Náströnd: those guilty of murder, adultery, and oath-breaking, which Norse society considered among the worst possible.
In the standardized Old Norse orthography, the name is spelled Níðhǫggr, but the letter ǫ is frequently replaced with the Modern Icelandicö for reasons of familiarity or technical expediency. The name can be represented in English texts with i for í; th, d or dh for ð; o for ǫ and optionally without r as in Modern Scandinavian reflexes. The Modern Icelandic form Níðhöggur is also sometimes seen, with special characters or similarly anglicized. The Danish forms Nidhug and Nidhøg can also be encountered; or NorwegianNidhogg and SwedishNidhögg.
According to the Gylfaginning part of Snorri Sturluson's Prose Edda, Níðhǫggr is a being which gnaws one of the three roots of Yggdrasill. It is sometimes believed that the roots are trapping the beast from the world. This root is placed over Niflheimr and Níðhǫggr gnaws it from beneath. The same source also says that "he squirrel called Ratatoskr runs up and down the length of the Ash, bearing envious words between the eagle and Nídhǫggr ." In the Skáldskaparmál section of the Prose Edda Snorri specifies Níðhǫggr as a serpent in a list of names of such creatures: Snorri's knowledge of Níðhǫggr seems to come from two of the Eddic poems: Grímnismál and Völuspá. Later in Skáldskaparmál, Snorri includes Níðhǫggr in a list of various terms and names for swords.
The poem Grímnismál identifies a number of beings which live in Yggdrasill. The tree suffers great hardship from all the creatures which live on it. The poem identifies Níðhǫggr as tearing at the tree from beneath and also mentions Ratatoskr as carrying messages between Níðhǫggr and the eagle who lives at the top of the tree. Snorri Sturluson often quotes Grímnismál and clearly used it as his source for this information. The poem Völuspá mentions Níðhöggr/Níðhǫggr twice. The first instance is in its description of Náströnd. Níðhöggr/Níðhǫggr is also mentioned at the end of Völuspá, where he is identified as a dragon and a serpent. The context and meaning of this stanza are disputed. The most prevalent opinion is that the arrival of Níðhǫggr heralds Ragnarök and thus that the poem ends on a tone of ominous warning. It could be, however, as the prevalent themes of Norse mythology are those of change and renewal, that this could be a 'redemption' of the serpent, 'shedding' the corpses and beginning life anew, much like a macabre Phoenix, or perhaps, lifting the bodies of the righteous rulers mentioned two stanzas before, so that they can dwell in Gimle, and then either Níðhǫggr sinks, or the völva sinks, depending on the translation, and the poem ends. Níðhǫggr is not mentioned elsewhere in any ancient source.
The Nidhogg appears in games such as Fate of the Norns,'Tower of Saviors,Age of Mythology,Final Fantasy XI,Final Fantasy XIV,Megami Tensei,World of Warcraft, Ragnarok Online, and the 2014 indie fencing game Nidhogg, as well as its 2017 sequel, Nidhogg 2. Although not in the game, Nidhogg is shown as a comparison for Alduin, the main antagonist of, in the sense both feed on the dead and are the symbols of destruction. In Alduin's case he feeds on the souls of the dead in Sovngarde, the afterlife of the natives of Skyrim and is prophecised to bring the end of the world, gaining the title World-Eater which could be a reference to Nidhogg's gnawing at the roots of Yggdrasil. In Eve Online, a class of capital ships, the Minmatar carrier, are called Nidhoggur. The Minmatar Republic in the game often uses Norse mythology in ship class names, such as Loki, Hel, and Ragnarok. Nidhogg is the subject of the song "On a Sea of Blood" from the album Jomsviking by Swedish melodic death metal band Amon Amarth. Another reference, albeit small, is the 50% form of Zygarde, a serpentine style Pokémon known as the Order Pokémon. This goes along with Xerneas, the Life Pokémon, being the stag of life, Dvalinn, and Yveltal, the Destruction Pokémon, being Hraesvelgr. Niðhöggr appears in Ichiei Ishibumi's light novel series High School DxD. Nidhogg appeared in 2014 manga To The Abandoned Sacred Beasts as a giant muscular dragon with a great life-force and abilities of attack and defence, incarnated in special soldier "John William Bancroft" who used his monstrous ability during the civil war on the government's side. After the war he returned as a war hero, but lost the ability to return to his human form thus losing his humanity slowly to his monster side. Later he was killed by his former Captain "Hank Henriette". Nidhogg is also the name of a bow in both ' and Fire Emblem Heroes. Nidhogg appears as a monster in the fantasy book by Michael Scott. In the Korean manhwa,, Nidhogg is featured as the Queen of Dragons who is able to destroy an army of Titans under the control of Valkyrie Sarah Irine. It also appears in the Korean web novel The Book Eating Magician. Nidhogg's eye is the button found in a carving of Yggdrasil the Red Skull pushes to reveal the Tesseract in the Marvel film. In 2018 Philippine TV SeriesVictor Magtanggol, Nidhogg is a type of serpent with small arms and bat-like wings. He is Loki's pet, adviser, messenger and right hand which tell him what to do and how to help him defeat his enemies. Niðhöggr is seen gnawing the root of Yggdrasil in the 2015 game Jotun during a section of the game taking place in the roots of Yggdrasil Nidhogg appears as a sub-boss in the Roots of Yggdrasil in the 2018 game La-Mulana 2. In the 2019 video game Devil May Cry 5, the Nidhogg parasite helps you progress through the story by killing parts of the demon trees roots. This may be a direct reference to the Yggdrasil and how Nidhogg eats its roots. Nidhogg is also a boss fight in this video game. In the anime series Soul Eater, Nidhogg is the name of the ghost ship captained by The Flying Dutchman villain. In the belly of the ship, a large amount of souls are stored and the character Ragnarok arrives to eat the souls.