The Celtic Otherworld

Contemporary literature on Celtic religion and folklore often equates the Celtic Otherworld with the realms of fairies or faeries. In both Welsh and Irish traditions the Otherworld was generally believed to be located either on an island or under the earth.

Where does the term Faerie come from?

In modern usage, the term “fairy” encompasses various spiritual beings, including elementals, plant devas, tricksters, household elves, and wood sprites, among others. These entities are often associated with supernatural realms and powers. However, when discussing “fairies” in Celtic countries, the response may differ. While there are supernatural beings referred to as “fairies,” they typically denote a specific type of entity known by various names such as “The Good People,” “The Good Neighbours,” or “The People of Peace,” among others.

The term “fairy” originates from the Old French “fairie,” meaning “enchantment or magic,” which evolved from the Latin “fata,” specifically referring to the Fates. The spelling “faerie” was introduced by Edmund Spenser in his work “The Faerie Queene,” of 1590, originally signifying a state of enchantment before being associated with beings possessing magical powers.

The etymology of these terms can be traced back to an Indo-European root word meaning “to speak,” highlighting the significance of language in magical practices. In Celtic tradition, the earliest references to pre-Christian spiritual entities come from Irish manuscripts, where they are known as the síabhra or the Áes Síde, meaning “the People of the Síd,” with “síd” referring to the Celtic Otherworld. This term, popularized as “sidhe” by William Butler Yeats, originally denoted the abode of the gods and was associated with pre-Celtic burial sites, which later became linked with fairy mounds in Celtic mythology.

The Irish Otherworld

In Irish mythology, the Otherworld has various names.  It is perhaps best known as Tír na nÓg or “the Land of Youth” but also Tír nAill (“the other land”), Tír Tairngire (“land of promise/promised land”), Tír na nÓg (“land of the young/land of youth”), Tír fo Thuinn (“land under the wave”), Tír na mBeo (“land of the living”), Mag Mell (“plain of delight”), Mag Findargat (“the white-silver plain”), Mag Argatnél (“the silver-cloud plain”), Mag Ildathach (“the multicoloured plain”), Mag Cíuin (“the gentle plain”), and Emain Ablach (possibly “isle of apples”). It is described as a supernatural realm where there is everlasting youth, beauty, health, abundance and joy, and where time moves differently. It is the dwelling place of the gods (the Tuatha Dé Danann) as well as certain heroes and ancestors.

The term síd, besides denoting Otherworldly locations, was used to describe the inhabitants of the Celtic Otherworld, known as the Áes Síde or “People of the Otherworld.” These divine beings, residing in síd mounds and watery locations such as rivers, lakes, and springs, were the ancient gods and goddesses of Ireland. Contrary to the diminutive fairies of modern folklore, the Áes Síde were depicted as spiritual entities possessing immense wisdom, power, and skill. In medieval texts, they were also identified as the Tuatha Dé Danann, the “Tribes of the Goddess Danu,” associated with land, sovereignty, and abundance.

Described in early Irish sources, the inhabitants of the Celtic Otherworld were depicted as fully human-sized beings, often exuding remarkable beauty and wearing magnificent jewelry and garments. While their true nature might not always be recognized by humans, they possessed a distinctive aura. In the Irish tale “The Wooing of Étain,” for instance, a king encounters an extraordinary woman bathing near a silver basin adorned with golden birds. This woman, with her golden hair and silver-gold comb, adorned in vibrant attire and jewelry, exhibited a striking appearance reminiscent of the Otherworldly beings.

An early poem in Old Irish portrays the inhabitants of the Celtic Otherworld as striking and formidable beings. Described as a supernatural assembly, they carry white shields adorned with pale silver emblems, wield glittering blue-grey swords and mighty horns, marching ahead of their chieftain and scattering their foes. The Áes Síde are characterized by their pale visages and fair hair, possessing smooth bodies, bright eyes, pure shining teeth, and thin red lips. Renowned for their great strength, they are skilled in battle and adept at playing fidchell, an early board game. Additionally, they are depicted as melodious in the mead hall and proficient at composing songs. Such was the perception of the early Irish regarding their native pagan deities.

While the Celtic fairy realms remained distinct from our world in both temporal and spatial dimensions, it was believed that they existed simultaneously alongside our reality. The Otherworld was perceived as the wellspring of wisdom, skill, truth, healing, and power. Within the Celtic Otherworld realms, there were elements of beauty or desirability reminiscent of our world, yet interwoven in an almost ethereal manner. Here is an excerpt from a poem found in the Irish tale Serglige Con Culainn (“The Wasting Sickness of Cú Culainn”), illustrating the wonders of the worlds concealed within the síd mounds.

There are, in the doorway to the west, in the place in which the sun sets
A herd of horses with speckled manes, and another chestnut herd
In the doorway to the east are three sacred trees of bright purple from which
A gentle, everlasting flock of birds calls to the offspring of the royal fortress.
There is a tree in the doorway of the court, not unseemly the nuts from it
A tree of silver that shines as the sun with a brightness like that of gold…
There is a vat of intoxicating mead that pours out for the folk there
It exists yet, enduring is the custom, so that it continues, ever- full.

In the Irish tale “The Voyage of Bran,” a woman from the Otherworld encounters the young hero, whose name translates to “Raven.” She paints a vivid picture of her realm, where grief, sorrow, sickness, and death are unheard of, and wailing and treachery are absent, replaced only by the sweet sounds of music. As she approaches him, she carries an apple branch, seemingly symbolizing passage or extending an invitation to traverse between the worlds.

A branch of the place of apple trees in Emain
I bring, like those that are familiar
Twigs of white- silver on it
Brightly fringed with blossoms
There is an island in the distance
Radiant around the path of sea- horses
A shining course towards bright- sided waves
Four feet sustain them
Feet of white bronze underneath
Gleaming throughout the exquisite worlds
A fair land throughout the ages of the seas
On which many blossoms fall
Glistening is the appearance of every colour
Throughout the gentle winds of the plain…
From its view, a shining tranquility
Of no comparison is existence out of the mist.

In Celtic mythology, the denizens of the Otherworld engage with each other and with mortals, often exhibiting benevolent behaviour in their interactions with humans. However, they may also test or challenge individuals, appearing in their path to entice or guide them into encounters with the Otherworld. If deemed worthy based on qualities such as truthfulness, courage, loyalty, or wisdom, the Áes Síde may bestow upon them gifts from the Otherworld, such as wisdom, skill, abundance, guidance, or protection.

In “Cormac’s Adventures in the Land of Promise,” King Cormac ventures away from his fortress and finds himself in a quintessential Otherworld encounter. A dense mist envelops him in the midst of a plain, leaving him standing alone. Ahead, he spots a grand fortress encircled by a wall of bronze. Inside, a house crafted from white silver and thatched with the wings of white birds catches his eye.

As Cormac enters the fortress, he discovers a radiant fountain from which five streams flow, each taken in turns by the inhabitants to drink. Nine hazel trees loom over the well, dropping their nuts into the water, while five salmon crack open the shells, allowing them to drift downstream. Described as more melodious than any human music, the sound of the cascading streams enchants Cormac.

A striking warrior approaches Cormac, leading him on a tour of the realm. Eventually, the warrior reveals himself as the god Manannán mac Lir, sovereign of the Land of Promise. He explains that he brought Cormac to the Otherworld to behold this land and unveils the fountain as the Fountain of Knowledge. The five streams represent the senses through which knowledge is acquired, emphasizing that true wisdom can only be attained by drinking from both the fountain and the streams—a privilege reserved for the People of Many Arts.

In an ancient Irish poem detailing the attributes of the Otherworld, a member of the Áes Síde extends an invitation to a mortal to journey into the Celtic Otherworld realms.

Blessed friend, will you come with me, to a land in which music is found?
Hair is like the blooming primrose there, and the colour of snow is every body.
There is neither “mine” nor “yours” here, teeth are bright, and brows are dark
A delight to the eye is our host, the colour of foxglove is every cheek.
Every neck like the pink field flowers, a delight to the eye are blackbirds’ eggs
Though very beautiful is Mag Fáil, it is a desert compared with Mag Máir.
Though the ale of Inis Fáil is intoxicating, more intoxicating is the ale of Tír Máir
A wondrous land, the land I speak of; youth does not follow the age of elders…
A distinguished people without blemish, conceived without sin, without guilt
We see everyone on every side and no one sees us.


Centuries later, in the folklore of the Celtic nations, the denizens of the Otherworld realms retained similar descriptions. They continued to reside in fairy mounds or near bodies of water, and their ability to either bless or challenge mortals persisted. Their inclination to assist was greater if their dwellings, customs, and traditions were respected, and akin to the gods, they could grant gifts of wisdom, skill, abundance, protection, fertility, or good fortune.

In Ireland, these beings, known as the “fairy folk,” were called the Síogaí or Na Daoine Maithe (“The Good People”). In Scottish Gaelic, they were referred to as the Sìtheachain or the Daoine Sìth (“People of the Síd mounds”). In Wales, they were known as the Tylwyth Teg (the “Beautiful or Fair Folk”) or Plant Annwn (the “Children of Annwn”). The Irish and Scottish Gaelic terms for the inhabitants of the Otherworld (Síogaí in Irish, Sìthechain in Scottish Gaelic) stemmed from the same root as the Old Irish word síd, retaining the same name, habitations, and nature as the old gods and goddesses.

The Old Irish word síd or síth may hold the key to understanding the deeper significance of the Áes Síde. It referred to the seat or location of the inhabitants of the sacred realms, as well as to those divine beings themselves and the magical, supernatural, and wondrous qualities of their world. Another meaning of síd or síth was “peace, goodwill, a state of peace,” possibly derived from the first word. While it didn’t denote the peaceful nature of the Áes Síde or the fairies, it represented the peace that could result from maintaining a right relationship with them.

The Otherworld often served as a model for human behaviour. In Celtic tales, its inhabitants guided or tested people and formed alliances with them. Relationships were initiated by the Tuatha Dé Danann or Plant Annwn, and encounters were determined by them. In tales like “Pwyll, Prince of Dyfed,” the heroes sought to gain peace with the Otherworldly beings. Recognizing the sacred identity of these beings and respecting their wisdom and power was crucial for humans to develop the right relationship with them. This path was based on truth and honour, offering potential blessings, teachings, obstacles, and challenges set by the Áes Síde. Respecting the gods and their wisdom allowed mortals to transcend their limitations and access divine gifts from the sacred realms.

The Welsh Otherworld

Meanwhile, Welsh tradition referred to the Otherworld as Annwfn or Annwn, signifying either the “Not-World” (i.e., the “Other” World) or the “Very Deep World,” specifically alluding to the Underworld. In Welsh mythology, the Otherworld is usually called Annwn or Annwfn. The word is derived from derived from an (‘in, inside’) and dwfn (‘world’).

Castles and Courts of Annwn

In the The First Branch of the Mabinogi: Pwyll Pendeuc Dyfed the story revolves around Pwyll mistakenly provoking Arawn, the sovereign of Annwn, by interfering with a hunt. This mishap occurs when Pwyll sets his own hounds on a stag already downed by Arawn’s pack. To make amends, Pwyll agrees to switch places with Arawn for one year, during which time he successfully vanquishes Arawn’s adversary, Hafgan. Pwyll describes Arawn castle in Annwn as follows:

So he went forward to the Court, and when he came there, he beheld sleeping-rooms, and halls, and chambers, and the most beautiful buildings ever seen. 

The First Branch of the Mabinogi: Pwyll Pendeuc Dyfed

This is similar in description to St Collen when he visited the court of Gwyn ap Nudd, located near to Glastonbury Abbey.

And when he came there, he saw the fairest castle he had ever beheld

Life of St Collen

In “The Book of Taliesin,” the poem “The Spoils of Annwn” (also known as “Preiddeu Annwfn”) describes a daring but ultimately futile expedition led by Arthur to plunder the Otherworld, Annwn, in quest of a magical cauldron. This poem my portray eight mystical islands, each guarded by its own castle but probably one castle with different names. In the poem the following line is repeated for each castle. “Except seven, none returned from Caer…”. The names of the forts are:

  • Caer Siddi [Faery Fortress]
  • Caer Pedyrvan [Four-cornered Castle]
  • Caer Vedwyd [Castle of Carousal]
  • Caer Rigor [Kingly Castle]
  • Caer Wydyr [Glass Castle]
  • Caer Golud [Castle of Frustration]
  • Caer Vandwy [another name for otherworld]
  • Caer Achren [another name for otherworld]

One of these castles, Caer Vandwy is also mentioned in The Dialogue of Gwyn ap Nudd and Gwyddno Garanhir:

Polished is my ring, golden my saddle and bright
To my sadness
I saw a conflict before Caer Vandwy.

The Dialogue of Gwyn ap Nudd and Gwyddno Garanhir

The People of Annwn

Again we can draw on the Life of St Collen and Pwyll Pendeuc Dyfed to find:

and the host was the most comely and the best equipped that he had ever seen. And with them came in likewise the Queen, who was the fairest woman that he had ever yet beheld. 

The First Branch of the Mabinogi: Pwyll Pendeuc Dyfed

manned by the best-appointed troops ; and there were numbers of musicians with every manner of song, vocal and instrumental ; steeds with youths riding them, the handsomest in the world ; maidens of noble mien, sprightly, light-footed, gay-apparelled, and in the bloom of youth ; and every magnificence becoming the court of a sumptuous king

St. Collen and Gwyn ap Nudd

The Welsh tale of Branwen, daughter of Llyr ends with the survivors of the great battle feasting in the Otherworld, in the presence of the severed head of Bran the Blessed, having forgotten all their suffering and sorrow, and having become unaware of the passage of time. Annwn is ruled by the Otherworld kings Arawn and Gwyn ap Nudd.

Where is Annwn?

Annwn as described in Pwyll seems to be a palace within easy walking or riding distance of Glyn Cuch, which divided Pembroke from Carmarthenshire. It was not, apparently, visible at all times, but, like the magic kaer in Manawydan, like the castle of the Fisher King in Chretien de Troyes’s Conte del Graal,suddenly appeared in the midst of a terrestrial landscape.

A similar picture is given in the sixteenth-century Buchedd Collen Sant. The saint, being summoned to speak with Gwynn ab Nudd, King of Annwn and the faery folk, on the top of Glastonbury Tor, ascends the hill.

Annwn is here regarded, on the one hand, as the faery castle, usually invisible to mortals, but occasionally made visible in a familiar terrestrial setting, much as in Pwyll. It is somewhat surprising to find it set on top of a hill.

A poem in the Book of Taliesin (No. vnI) includes a phrase that translates to “in Annwn below the earth, in the air above the earth,” indicating a multi-dimensional concept of the mythical Annwn. Similarly, Dafydd ap Gwilym references Annwn in his description of a fox’s den, pointing towards this otherworldly realm. However, contrary to the notion of a gloomy underworld akin to Hades, two Welsh writers from the late 12th century, in Latin texts, depict Annwn as a somewhat dim yet enchanting land, populated by noble dwarfs and rich in treasures. The perspectives of Map and Giraldus Cambrensis on this are particularly noteworthy. The localization of Annwn is further detailed in our poem, where Arthur and his men, aboard the ship Prydwen, venture to Annwn via the sea, aligning with a description in another Taliesin poem that portrays Annwn as an island encircled by ocean currents.

Thus, it can be confidently stated that the ancient Welsh envisaged Annwn as either a mystical palace intermittently visible in the familiar landscape, a delightful underground realm, or a heavenly island. When Christian influences equated Annwn’s ruler with the devil, the realm took on hellish attributes, yet it continued to be seen as a place of beauty. Notably, Annwn was always famed for its hospitality and abundant treasures, especially precious vessels.