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Goldnail, the mighty sword, cries out for your blood! Come! Step forward so that I, the indomitable Blight, may cut you down!
Goldnail (「金釘」?; Kanakugi) was a sword that was used by the microscopic demon Blight. It had a stained blade and gave off a toxic green mist which was responsible for the illness that plagued Sei'an City. It was the source of Blight's life force.
Goldnail was used in many battles throughout history and had killed countless people[Citation needed]. The blade was drenched in the blood of its victims and eventually was infused with darkness and became a demon. At an unknown point in time, the sword gained independence and created Blight.
Goldnail and Blight split from Orochi's body after the serpent's defeat. The demon went to Sei'an City and worked with Ninetails to plunge Ryoshima Coast into darkness. Blight entered the Emperor's body and spread a poisonous fog that covered the entire city. Many of the city's residents fell ill and miniature Cursed zones covered the city, causing the trees to wither and the water to dry up. Blight took control of the Emperor and had Kaguya imprisoned.
With the help of the Lucky Mallet, Issun and Amaterasu entered the Emperor's body and found Blight. Having found the source of the poisonous fog, Amaterasu did battle with the demon. During the battle, Amaterasu discovered Blight's weakness, Goldnail. She attacked the sword and wore Blight down until the demon could take no more. After their defeat, the essence of Blight and Goldanil flew away to meet up with their demon brethren in the Ark of Yamato. Amaterasu finally laid its spirit to rest after a rematch in the ark.
Also, Goldnail bears resemblances to Vergil himself. Goldnail can summon a circle of swords around Blight, while Vergil has the ability Summoned Swords, which enables him to fire spectral blades, instead of usage of firearms. Also, Blight's swords circles bears very strong resemblances to Vergil's Spiral Swords, which is an extension of the Summoned Swords technique, in which Vergil creates a barrier of countless swords that surrounds his body.
Since Devil May Cry 3 was made before Ōkami, it is possible that Blight was modelled after Vergil. As an extra note, both possess extremely skilled swordsmanship.
↑"Blight, a disease residing within the Emperor's body and born of the intense hatred and evil of the cursed sword Goldnail, was the source of the acrid mist that had plagued the capital's citizenry."—Narrator (Ōkami)