Hellhounds

A hellhound is a dog of Hell, found in mythology, folklore and fiction. Hellhounds typically have features such as black fur color, glowing red eyes, super strength or speed, ghostly or phantom characteristics, and sometimes even the ability to talk. Hellhounds are often associated with fire, and may have fire-based abilities and appearances. They are often assigned to guard the entrance to the world of the dead or undertake other duties related to the afterlife or the supernatural, such as hunting down lost souls or guarding a supernatural treasure. As legend goes, if one happened to see the hellhound three times, he or she will die an abrupt and unseen death.

Powers and abilities
Enhanced speed 

Enhanced senses 

Invisibility 

Known hellhounds
Cerberus

Examples from folklore
The most famous hellhound is probably Cerberus, the hound of Hades from Greek mythology (This hellhound is usually described as translusent). Hellhounds are also famous for appearing in Celtic mythology as part of the Wild Hunt. These hounds are given several different names in local folklore, but they display typical hellhound characteristics. The myth is common across Great Britain, and many names are given to the apparitions: Black Shuck of East Anglia (which has its roots in the Norse mythology rather than that of the Celts), Moddey Dhoo of the Isle of Man, Gwyllgi of Wales, and so on. See Barghest. The earliest mention of these myths are in both Walter Map's De Nugis Curialium (1190) and the Welsh myth cycle of the Four Branches of the Mabinogi (ca. 10th-13th century)

In Southern Mexican and Central American folklore, the Cadejo is a black dog that haunts naughty young men who walk late at night on rural roads. The term is also common in American blues music, such as in Robert Johnson's "Hellhound on my Trail".

It also appears in the Percy Jackson and the Olympians series multiple times, whether or not this creature is friend or foe.

Appearances
"Crossroad Blues."

"No Rest for the Wicked"

"Abandon All Hope..."