Claíomh Solais

This characterization is inspired by the formula where the hero gains a beautiful wife (and riches) by gambling against a gruagach aka wizard-champion, but suffers losses which makes him beholden to mount on a hopeless-seeming quest.

Like the actual "giant's daughter" bridal quest tales, the sword of light hero often gains assistance of "helpful animals" in completing his tasks or ordeals.

The sword has been regarded as a legacy to the god-slaying weapons of Irish mythology by certain scholars, such as T. F. O'Rahilly, the analogues being the primeval Celtic deity's lightning-weapon, Lugh's sling that felled Balor, the hero Cúchulainn's supernatural spear Gae bulga and his shining sword Cruaidín Catutchenn.

[e][12] and the sword's keeper is often a giant[17][18] (athach,[1] Scottish Gaelic: fhamhair[19]) or hag (cailleach),[21][17] or a sibling of the wizard.

[26][27] The hero in some examples are compelled to perform (three) sets of tasks, aided by helpers, who may be the would-be bride,[29] "helpful animals",[f][32] or a supernatural being ("little green/red man").

[92] The werewolf tale, recounted by a man who had once been magically transformed into a wolf by an unfaithful wife, is analyzed by Kittredge for its compound structure, but the in-tale generally does not concern the Sword of Light.

In "The Thirteenth Son of the King of Erin", Sean Ruadh (actually the eldest prince) is assisted by the princess who is his would-be bride in slaying the urfeist (sea-serpent).

[10] Josef Baudiš suggested a slightly different grouping, which similar to the bridal-quest type but distinguishably different: the hero wins a beautiful wife (and riches) as wager in a game played against a gruagach (wizard-champion) figure, but it is a trap, and when the hero suffers a loss, he is compelled to go on a quest, usually for the sword of light.

[103][104] Kittredge considered the "secret about women" element to be an essential and original part of the Irish story, as seen in the stemma of texts given by him,[ab] even though the "woman" part of it has been lost in some variants, such as Kennedy's Fios Fath an aon Sceil ("perfect narrative of the unique story")[105] A more familiar Arthurian tale perhaps than Arthur and Gorlagon which embeds the quest of "What is it that women most desire?"

[24] The tale "The Young King Of Easaidh Ruadh" was also given as a typical example of "External soul" motif (E 710[107]) by folklorist Katharine Mary Briggs.

[25] It has been pointed out that the Easaidh Ruadh refers to a place name in Ireland, probably the Assaroe Falls in Ballyshannon, County Donegal.

[28][114] The assertion has been made that Claidheamh Soluis is "a symbol of Ireland attributed in oral tradition to Cúchulainn" (James Mackillop[3]), although none of the tales listed above name Cuchulainn as protagonist.

[118][119] A broad sweeping parallel has been made between the light or lightning weapons of Celtic tradition and King Arthur's Excalibur, described as brightly shining in several places of the Vulgate cycle Roman de Merlin.

[122] The episode has been copied by Malory as well[122] (with the knight being called Accolon unlike the French original)[123] Dáithí Ó hÓgáin deduces that certain properties of the sword of light (such as screaming when touched in order to alert its owner) is likely borrowed from Arthurian material, because there is evidence that a version of Fios Fatha an Aonsceil ('the knowledge of the cause of the One Story') had been told about Gearóid Iarla (Earl Gerald FitzGerald) of the 14th century, whose family had close ties with Arthurian tradition.

[124] To the Earl is attached a Barbarossa legend (King asleep in mountain motif),[125] which makes the figure conducive to be transformed into a "sleeping giant" of folktale.

Definitive 6-pence stamp of Sword of Light, Ireland, 1922–3. Arched caption reads "An Claiḋeaṁ Soluis"
The King of Ireland's Son thrusts the sword of light.
Willy Pogany illustr., frontispiece of Padraic Colum , The King of Ireland's Son (1916).