Celtic tales are full of heroic warriors and mystical gods. They are also the origin of Halloween's (and Ireland's) preoccupation with the 'little people'.

Academics have concluded that the little people were, originally, the pagan gods of Ireland who lost their significance and, metaphorically, their stature, when Christianity arrived.

Despite their reduced state and retirement to the Underworld as fairies, a memory of their magical powers held fast in the imagination of the people. Here lies the origin of Halloween's dark side.

There are two main groups of fairy: the trooping fairies who are, for the most part, friendly and have healing powers, and the solitary fairy who causes mischief and is quick to anger.

Among the specific terrors of Halloween were the Fomorians who believed they had a right to take back to the Otherworld their share of fresh milk, grains and live children.

The Leprechaun is the best known of the latter group.

The fairy most connected with the origin of Halloween is the Puca (pronounced Pooka) who is decidedly malevolent and capable of assuming any shape. The puca is particularly adept at taking animal shapes, especially horses, so riders beware on Halloween – your 'steed' may not be under your control!

The Banshee is another fairy, always female, who warns of approaching death by letting loose a terrible, eerie wail (the Banshee scream) that is guaranteed to send a shiver down the spine of those that hear it. If you hear the cry of the Banshee of Ireland, you should look out for a funeral carriage pulled by a headless horse.

To ward off the evil let loose at Samhain, huge bonfires were lit and people wore ugly masks and disguises to confuse the spirits and stop the dead identifying individuals who they disliked during their own lifetime.

They also deliberately made a lot of noise to unsettle the spirits and drive them away from their homes. The timid, however, would leave out food in their homes, or at the nearest hawthorn or whitethorn bush (where fairies were known to live), hoping that their generosity would appease the spirits.

For some, the tradition of leaving food (and a spoon to eat it!) in the home – usually a plate of champ or colcannon – was more about offering hospitality to their own ancestors.

Just as spells and incantations of witches were especially powerful at Samhain, so the night was believed to be full of portents of the future.