Also called the Hellhound and a Warg, the Freybug is something of a demonic canine from medieval English folklore. Perhaps the most famous Hellhound is Cerberus from Greek mythology. This is the three-headed dog who stands as the keeper to the gates of Hell. Milton even included him in his epic poem, Paradise Lost, which I recommend reading if you have the patience.
The twelfth labor of Heracles was to bring back Cerberus. Here are two selections which portray this.
On a more personal note, my oldest daughter owns a rescue dog whom she named Cerberus (Cerbie for short). Despite her large size and ominous name, she’s actually an amiable pooch.
As a final offering for your viewing pleasure, here is the rendering of a Freybug by William O’ Connor from his Dracopedia: The Bestiary.