Hellhounds

"Hellhounds - the demonic pit bulls of Hell."

Hellhounds are supernatural ballistic and maniacal demonic dog beasts of the supernatural, which are known to serve demons. Described as demonic pitbulls, Hellhounds are ferocious, terrifying entities that inspire fear in humans, demons, monsters, and  angels. A wide variety of ominous or hellish supernatural dogs occur in mythologies around the world, similar to the ubiquitous dragon.

With time they became tasked with collecting the souls of humans whose deals are come due. In such circumstances, hellhounds can only be seen by those whom they have come for, making them a sort of Reaper of the damned. In later seasons, hellhounds are seen working for other demons (not just Crossroads demons), usually acting as foot soldiers, guard dogs and/or assassins.

According to Crowley, no demon knows the hounds better than him. As the "Demonic pit bulls" of Hell, Hellhounds are also one of the most recurring supernatural creatures in the series.

Powers and Abilities
Hellhounds possesses many supernatural abilities, as a result of their demonic origins. While insubstantial under normal circumstances, Hellhounds are able to assume a corporeal form.
 * Invisibility: Hellhounds are invisible to humans, except under special circumstances. However, many supernatural creatures, such as demons and angels, can see them. They can also be seen by the humans they are assigned to hunt and through an object scorched with Holy Fire.
 * Invulnerability: Hellhounds cannot be killed by conventional means or weapons. However, weapons like Ruby's Knife, or an Angel blade, can kill them.
 * Super senses: Just like any supernatural creature, their senses are extremely keen.
 * Super speed: They are naturally much faster than humans.
 * Super stamina: Once a hellhound has the scent of its prey, it will never stop hunting him or her, unless it is killed or called off by its master.
 * Superhuman Strength: Hellhounds are stronger than and are able to overpower and kill humans, even demons, and possibly angels. They can easily knock down and overpower humans with little difficulty.
 * Superhuman Endurance: Hellhounds are incapable of being harmed or slain by all forms of conventional injury, including firearms or blades. Furthermore, these beasts cannot feel the pain that would result from such attacks.
 * Hellfire Breathing: They are able to breathe hellfire in either form, burning his victims’ souls.
 * Fangs and Claws: Hellhounds are able to deliver a powerful bite and inflict scorching gashes with their black claws.
 * Probability Manipulation: Hellhounds are harbingers of death, and those who are unfortunate enough to encounter them are fated to die or meet with great misfortune within a year’s time. Looking into the Black Dog’s fiery eyes means certain death within a year, and attacking the Hellhound will bring about fatal consequences.
 * Fear Inducement: These demonic spirit dongs are able to induce feelings of overwhelming terror in a victim through their malicious glare alone, oftentimes causing total bodily paralysis (although this effect is only temporary).
 * Affliction: If attacked, Hellhounds are able to inflict savage, excruciatingly painful wounds, which are slow to heal (if the wounds heal at all).
 * Precognition: They seem to be able to predict the deaths of people, often appearing before someone dies and howling when someone is knocking at death’s door.
 * Intangibility: Hellhounds are seemingly impervious to physical attacks. Bullets, blades, and fists pass through the spirit’s ethereal body completely.
 * Superhuman Intelligence: Despite their ferocious animal nature, Hellhounds are exceptionally intelligent, able to anticipate the actions of eyewitnesses and counter them (in one instance, an attacker who tried to kick the Hellhound found his foot in the spirit’s mouth).
 * Teleportation: They are able to dematerialize and disappear at will, as well as render themselves completely invisible. Travelers can still feel the Hellhound’s sinister presence, even if he has disappeared.
 * Body Manifestation: The power of a nonphysical being to become physical.
 * Tracking: They can locate any human or demon they are sent after.
 * Hallucinations: When close to their prey, hellhounds cause their victims to experience hallucinations, so as to frighten them out of hiding and leave them defenseless.