Viggo's Fire Sword

"I liked your fire sword so much, I made my own with improvements, of course."

- Viggo

Viggo's Fire Sword is Viggo's main weapon during the episode Triple Cross.

Dragons: Race to the Edge, Season 6
Having been inspired by Hiccup's Inferno, Viggo made himself a sword that can ignite itself. He briefly used it against Hiccup, with the fight ending when Viggo released gas from the sword and ignited it, making a small explosion. Viggo then put his sword down as a sign that he doesn't want to hurt Hiccup.

Later, when Johann figured that Viggo is not on his side anymore, the latter released gas and ignited it, creating a big explosion to mask his escape. He then found his Skrill and freed him by cutting its chains with his sword. Viggo is seen with his sword in his hand while talking to Hiccup. As his final act, Viggo ignites the sword and attacks a group of Dragon Hunters.

Design
Viggo's fire sword is nearly identical to Inferno's design from the second film, which was probably inspired from it. The handle, however, is similar to the handle of Viggo's normal sword, being encrusted with jewels. The part that releases gas has the shape of the head of a dragon. Due to the fact that it was able to cut dragon-proof metal, it is presumed that the sword is made out of Gronckle Iron.

Abilities
As Viggo mentioned, although this sword was inspired from Inferno, it has some improvements. Igniting: Just like Hiccup's Inferno, Viggo's fire sword is covered is Monstrous Nightmare saliva, allowing the sword to be set aflame when ignited.

Gas: Viggo's fire sword contains Zippleback gas in its handle, which can be released when a certain button is pressed.

Trivia

 * Hiccup's design for Inferno in How to Train Your Dragon 2 is almost identical to Viggo's fire sword:
 * Both have blades made out of thin metal, forming only the edges of the sword.
 * Both have handles that have the shape of the head of a dragon.
 * Both can release Zippleback gas and sparks to ignite it.