These large pots, used in various rituals by the Celts, become enchanted objects in several episodes in Welsh legend. The nature of the cauldrons and the warriors’ quests for them have been seen by some as precursors of the Grail and the Grail Quest.
The earliest Arthurian poem, called The Spoils of Annwn, describes Arthur’s expedition to the Welsh Otherworld, where he obtains a magic cauldron (“gently warmed by the breath of nine maidens”, the maidens here preceding the Grail maidens of later legend) that would not “boil a coward’s food”.
Arthur similarly obtains such a cauldron in Culhwch and Olwen, after he invades Ireland and kills Diwrnach the Irishman. Diwrnach’s cauldron is mentioned among the Thirteen Treasures of the Island of Britain: as suggested by Annwn, it would only boil food intended for a brave man (this ability to separate the brave from the cowardly mirrors the Grail’s ability to divide the pure from the perfidious).
An invasion of Ireland similar to the one in Culhwch occurs in the non-Arthurian tale of Branwen. Here, the British king is Bran the Blessed. The cauldron he obtains as part of his plunder had the power to resurrect the dead (healing is another property assigned to the Grail). The episodes in Annwn, Culhwch, and Branwen are similar, with Ireland suggesting the otherworld in the latter two.
In another legend, the bard Taliesin was said to have been born from a cauldron. Irish legend has its share of cauldrons as well, with the mythological god Dagda owning a cauldron of plenty (similar to the Grail in the First Continuation).
Preiddeu Annwfn | Attributed to Taliesin, c. 900
Culhwch and Olwen | Late 11th century
Triads of the Island of Britain (Welsh ”Triads”) | 11th century to 14th century