Fire Terrors are similar to normal Night Terrors, but they are red in color. All members have a grayish underbelly and an orange back. Their eyes are a glowing red, but faint slits for pupils can be seen.
Fire Terrors live in the caves inside Caldera Cay, and likely eat the fire produced from the lava. Like the regular Night Terrors, Fire Terrors live and hunt in packs, and they have a fierce instinct to protect the Eruptodon eggs, even from humans. They also share similar mannerisms as regular Night Terrors. Fire Terrors are known to consume fire, as seen when one ate the flames produced by Inferno. They later use this fire against their attackers by shooting it back.
These dragons are likely trained in a similar manner to a normal Night Terror. For the ones on Caldera Cay, it is possible they were once trained many years ago by Mala's family. Each generation of Fire Terrors passed on the trait of protecting the egg of the Eruptodon, as the drawing on the cave wall showed.
Fire Terrors made their debut in the episode "Out of the Frying Pan". The Dragon Riders and Mala must take an Eruptodon egg into the volcano at Defenders of the Wing Island since the Great Protector is not able to do so. While entering the volcano, the team discovers some murals depicting the Fire Terrors. The Fire Terrors themselves try to 'steal' the Eruptodon egg. Mala initially mistook the drawing as a warning against the Fire Terrors and thought they were trying to harm the egg. However Hiccup noticed their behavior "did not seem predatory" and ultimately it is revealed that the Terrors were actually trying to defend and protect it.