Hiccup’s fire sword can be used in battle against dragons. Hiccup first used it when he was captured by Dragon Thief Valka, and then again when he tried to pacify her dragons. Unfortunately, he did not succeed in this task. His next use of the fire sword was when he was fighting Drago Bludvist, and it knocked off the Bewilderbeast with Zippleback gas.
Inferno
Hiccup first creates the Inferno sword in the series while freeing a chicken from the Death Song. After preparing it with Monstrous Nightmare gel, Hiccup ignited the blade and used it to free the chicken. The result was an early prototype of the Inferno sword, which Hiccup later upgraded to a sword. Hiccup named it Inferno and Astrid suggested he make the blade twice as large.
The Inferno sword was a great asset to Hiccup during his adventure. He used it to scare off the Silkspanners and free Toothless from the dragonvine, as well as a crossbow. The Inferno is updated throughout the series, and Hiccup is constantly experimenting with it. Hiccup uses it to train with Astrid, and even uses it as a torch in his underground cave.
Hiccup also uses the Inferno to pacify dragons, which he uses when he is captured by a Dragon Thief. Unfortunately, his attempts to pacify the dragons were in vain due to the large number of dragons in his path. Using a Zippleback gas canister in his boot, he primed the Inferno and sprayed the blade in a circle around himself. This was effective in calming the dragons down and protecting Hiccup from harm.
https://www.youtube.com/watch?v=lsmy64p50T8
Calder
Calder is a mongrel from the tribe of the stormhearts. He is the younger brother of king stormheart and the original heir to the throne. He was bred for both physical strength and tactical intelligence. He underwent many trials and tribulations against dragons as part of his training. His tribe also worked with the dragon trade industry, but he never approved of their behavior and sought to free the tribe from it.
Hiccup wielded a fire sword known as the Inferno. It is a retractable blade that can become inflamed by contacting a hot surface. Hiccup used this ability to intimidate humans. The Inferno has two lighters on the end of the blade that can ignite both Hideous Zippleback gas and the Hideous Zippleback saliva.
Hiccup also added a second Nightmare gel canister to the Inferno sword. He used it more often in combat than in the other movies. The sword was a useful tool for training with Astrid and later, during the Dawn of Destruction, when Hiccup and Astrid needed to free the dragon from the amber. Hiccup also used it as a torch in an underground cave.
Monstrous Nightmare saliva
Hiccup is an adventurous and fearless dragon trainer, but sometimes his adventures will bring him into contact with new and dangerous dragons. To deal with these situations, Hiccup has invented a device that imitates dragon fire. One end coats itself with flammable Monstrous Nightmare saliva and the other end explodes with explosive Hideous Zippleback gas when ignited by a built-in lighter. With this device, Hiccup is able to train any dragon with little effort.
Hiccup created the Inferno sword during his rescue mission from Death Song. Using the Monstrous Nightmare gel to hypnotize the victim, he ignited the knife, which became the first prototype of the Inferno sword. When Astrid saw the knife, she suggested Hiccup make it twice as large as its original blade. Hiccup later upgraded his creation into a sword.
Toothless
Hiccup has a very powerful fire sword. Using it, he can tame strange dragons in a matter of seconds. He also uses a kneeling spin to spray flammable gas, which helps him convince them he’s actually a dragon. This is an impressive feat, especially given that he lost a foot five years ago.
Toothless has protruding scales on its back, allowing it to make sharper turns. This makes it more powerful than the dragon Hiccup had before. Hiccup also uses this fire sword to free the dragon Stormfly, which is ensnared in the net.
Hiccup also created a fire sword, called an “Inferno.” This fire sword is retractable and inflamed and was forged to pacify wild dragons. It also helps Hiccup cut hardened Death Song amber. It is also equipped with two lighters, which ignite Hideous Zippleback gas and Nightmare saliva.