The Hellhound, also known as the Cerebus, is an enemy in the original Final Fantasy. They appear as one of the most common enemies in the Mount Gulug, often appearing with Gigas type monsters. It is weak to Ice spell, as most of the enemies in the volcano, and absorbs the Fire spell. It may attack for low damage, or use Blaze, to hit all the allies for low damage (fire elemental). It is not hard alone, but as he appears in groups of more hounds, you may find out Ice spells spread out more, and they don't die very fast. Be persistent.