Fire-breathing monster

[3] Cacus was described by the Romans as a monstrous, giant fire-breathing son of Vulcan, who resided in a cave beneath the Palatine Hill prior to the founding of Rome, and was killed by Hercules after a tremendous battle in which the hero was attacked by the creature's fire breath.

[7] In Norse mythology, the sea serpent Jörmungandr is depicted as a fire-breathing creature, similar to a dragon, with smoke coming from its nostrils in Nordic lore.

In Philippine mythology, the sea serpent Bakunawa, known in Visayan folklore as the moon eater, is described as kindling coal and emitting flames from its mouth at night.

A winged monster believed to have a body like that of a crocodile or snake and spit fire called Ninki Nanka appears in West African folklore.

[9] The Hobbit and The Lord of the Rings, seminal works of fantasy fiction by J. R. R. Tolkien, prominently included powerful fire-breathing monsters, such as Smaug the dragon and the Balrog.

An artistic depiction of a mythical dragon in the process of breathing fire.
The Balrog in The Lord of the Rings and associated works is depicted as a demon with the ability to breathe fire.