Hell Hound

In essence, a hell hound is the demonic relative to the common wolf. Unlike natural wolves, however, hell hounds are malevolent, and are not interested in being your friend - only in spreading fire, an interest they pursue readily by breathing forth bursts of flame. Even their bite itself is enough to set creatures on fire.

Hell hounds can be found in the overworld, albeit rarely. They are significantly more common in the fiery pits of the Nether from whence they spawn, where their natural affinity for the inferno puts them right at home.

A hell hound's breath will not only set an area of 3x3 blocks on fire, but will destroy water source blocks, so just carrying around a water bucket will not save you.

Origin

The fire-breathing hell hound is taken from Dungeons & Dragons; here are the game stats for hell hounds. More generally "hell hound" or "hellhound" is commonly used for any supernatural dog of a hellish or demonic nature.