Demonic Swords

The Demonic Swords (魔剣 Maken) are weapons infused with Demonic power and are considered to be the ultimate weapons against Seraphs and Fallen Angels.

Summary
Not much is known about the Demonic Swords except that they have a strong curse placed on them which brings misfortune to their wielders.

The Ancient Gear Blade Borne has the ability to create Demonic Swords and Weaponry, but they are inferior to the original ones.

Abilities
Demonic Swords are the exact opposite of the Holy Swords, in which they use demonic power and are extremely powerful against Seraphs and Fallen Angels. Just as with the Holy Swords, only a select few can wield Demon Swords and they are known to even shorten the lifespan of its user if overused. Demon Swords appear to have a will of their own, as revealed in Volume 12, as Tomoe has stated she has begun talking to Balmung.

Known Demon Swords
Gram (グラム Guramu) also known as the Demonic Emperor Sword (魔帝剣, Mateiken). It was once wielded by the original Siegfried to kill one of the Dragon Kings, Fafnir before the latter was resurrected by the Norse gods. It is currently in possession of the exiled hero Arthur Pendragon.

Hrunting (フルンティング, Furuntingu), is a Demon Sword from Norse mythology. One of the strongest Demonic Swords in existence, known as the Tempted Emperor Sword (誘惑帝剣, Yūwakuteiken). It was previously used by the original Beowulf to slay the mother of the Evil Dragon Grendel. It is currently in possession of the ex-hero Siegfried.

Balmung (バルムンク Barumunku) is a Demon Sword from Norse mythology with a drill-like aura. It is capable of creating powerful whirlwinds and has dragon-slaying capabilites. It is one of the six demonic swords currently in possession of the hero Tomoe Nonaka.

Onimaru (鬼丸), is a Cursed Demon Sword from Japanese historical legend, possessed by the spirit of an Oni Demon. It has the ability to generate and control black flames, and move on its own. It is one of the six demonic swords currently in possession of the hero Tomoe Nonaka.

Dáinsleif (ダインスレイヴ Dainsureivu) is a Demon Sword that creates huge pillars of ice from the ground. It is one of the six demonic swords currently in possession of the hero Tomoe Nonaka.

Nothung (ノートゥング Nōtungu) is a Demonic Sword that specialises in sharpness, lightning control and dragon-slaying capabilities. It is one of the six demonic swords currently in possession of the hero Tomoe Nonaka.

Tyrfing (ディルヴィング Diruvingu) is a Demon Sword that specialises in destruction. It is one of the six demonic swords currently in possession of the hero Tomoe Nonaka.

Gambanteinn (ガンバンテイン, Ganbantein) is a Demon Sword with magical properties. It is one of the six demonic swords currently in possession of the hero Tomoe Nonaka.

Trivia

 * Balmung and Nothung are alternate names for Gram.
 * Dáinsleif, meaning "Dáinn's legacy" in Old Norse, was a sword wielded by King Högni in Norse mythology.
 * Tyrfing is the titular sword used in the Norse legend collection the Tyrfing Cycle. According to the legend, it was a sword forged by the Dwarves Durin and Dvalin. They are forced to do so by Svafrlami, the king of Gardariki, but in revenge they curse the sword so that it will kill a man every time it is unsheathed, cause three evil deeds and be the undoing of Svafrlami.
 * Hrunting is one of the two swords used by the hero Beowulf, given to him by Unferth, from the epic story of the same name.
 * Onimaru, meaning "Demon Circle", is a sword mentioned in a story from the epic Taiheiki, where it moved itself and killed an Oni Demon (which is where the name of the sword comes from), and cursed the man Hōjō Tokimasa. It is also one of the Tenka-Goken (天下五剣, "Five [Best] Swords under Heaven"), as a Imperial Property of Japan.
 * Currently all known Demonic Swords are not used against Seraphs, but mainly through Heroes, Vampyres, Demons, Fallen Angels, Dragons, Monsters, and other demonic beings of darkness.