There are numerous mythological references to  'hellhounds' in Greek, Indic, Celtic, Germanic, Latin, Armenian and Iranian sources. As scavengers and carrion-eaters, dogs came to be associated with death, in both the classical and Celtic religious traditions.

The cult is older than that of Osiris, and can be traced to the Sumerian goddess Bau who was also dog-headed. Her name may well be onomatopoeic, little removed from 'bow-wow'. Anubis himself, written in early heiroglyphs as 'An-pu', may be a direct continuation of Bau's father, the Sumerian god An.

In the early stages of Egyptian religion, at least, Anubis was linked with the star Sirius, the brightest star in the sky, known in most mythologies throughout the world as the 'Dog Star' and the central consideration of the Egyptian calendar - although Sirius was later most closely linked with Isis, of course. Incidentally, this is where our expression 'dog days' originated: the hot, parched season that followed the heliacal rising of Sirius coinciding with the Nile's annual inundation of the valley.

Dogs were closely linked with the Greek goddess Hecate (along with lions and horses). Indeed, at times she was depicted as dog-headed and was certainly linked to the Dog Star, Sirius. Her pet was the dog Cerberus (or Kerberos) who is the watchdog at the entrance to Hades.

A dog as companion on the road to the Otherworld occurs explicitly in one of the tales in that vast hindu epic the Mahabharata. Yudhishthira, the King of Pandavas, with his five brothers, their joint wife and a dog set off on a rambling journey which took them to the sacred 'omphalos' of the hindus, Mount Meru. The companions die one-by-one of exhaustion but Yudhishthira survives and 'enters heaven in his mortal body, not having tasted death' . The dog too comes with him, and is revealed to be Dharma (the Law) in disguise.

The Altaic shaman encounters a dog that guards the underworld realm of Erlik Khan. When the Yukaghir shaman follows the road to the kingdom of shadows, he finds an old woman's house guarded by a barking dog. In Koryak shamanism the entrance to the land of the dead is guarded by dogs. In Eskimo shamanism, a dog with bared teeth guards the entrance to the undersea land of Takakapsaluk, Mother of the Sea Beasts. The custom of burying a dog and the skin of a favourite reindeer with a dead man was still current among Ugrian people of Siberia earlier this century

Greyhounds are specifically mentioned in the early Welsh literature: they formed some of the many gifts presented to Pwyll by Arawn, lord of the Otherworld, in the First Branch of the Mabinogi. Two greyhounds accompany Culhwch, when he sets out in all his splendour to visit his cousin Arthur, in 'Culhwch and Olwen.'

Hellhounds almost abound in the northern myths - such dogs are mentioned in Baldrs Draumar, Voluspa, Gylfaginning, Grimnismal, Skirnismal and Fjolsvinnsmal.