The legendary character began life as Gwion Bach, a servant to Ceridwen, the wife of a nobleman Tegid Foel, in the days when King Arthur ruled.
Ceridwen had a beautiful daughter and an ugly son named Morfran, which means "Great Crow", whose appearance no magic could cure.
Ceridwen felt in order for him to gain respect and acceptance from noblemen he had to have great qualities to compensate for his ugly looks, so she sought to give him the gift of wisdom and knowledge.
A blind man, Morda, was assigned by Ceridwen to stir the cauldron, while Gwion Bach, a young lad, stoked the fire underneath it.
The first three drops of liquid from this cauldron would make one "extraordinarily learned in various arts and full of spirit of prophecy" (The Tale of Gwion Bach), and the rest was a fatal poison.
Exhausted, Ceridwen managed to force him into a barn, where he turned into a single grain of corn and she became a tufted black hen and ate him.
She resolved to kill the child, knowing it was Gwion, but when he was born he was so beautiful that she couldn't, so she had him put into a hide covered basket and thrown into the lake, river, or sea, depending on which version of this tale it is.
Elffin deg taw ath wylo na chabled neb yr eiddio ny wna lles drwg obaitho nid a wyl au portho nid a n goeg gweddi cynllo ny thyr duw yn addawo ni chad ynghored wyddno erioed gystal ac heno
Elffin deg sych dy ddau rudd nyth weryd bod yn rhybudd cyd tybiaist na cefaist ffudd ny wna lles gormod awydd nag ymaf wrthaf dofydd cans o for ag o'r fynydd ag o'n eigion afonydd I'r tri Dduw da i dwedwydd
Elffin gynheddfaf diddan anfilwriaidd yw damcan nid rhaid yt ddirfawr gwynfan gwell duw na drwg ddarogan gyd bwyd eiddill a bychan ar nod gorferwch mor dilan mi a wnaf y nydd gyfran wyt well na thri chant maran
Taliesin intervened just in time with a clever scheme that involved his mistress exchanging places with a scullery maid.
Rhun sat down to have dinner with the disguised maid, and when she fell asleep he cut off a finger of hers that wore Elphin's signet ring.
The tale of Taliesin ends with him telling prophecies to the Maelgwn about the origin of the human race and what will now happen to the world.
A close parallel outside Celtic mythology can be found in Saxo Grammaticus' Gesta Danorum (V.2.6-V.2.8, 12th c.), where Eric, son of Regnerus, acquired eloquence and wisdom by eating the snake-infested stew his step-mother Kraka had prepared for his half-brother Roller.
[1][2] Saxo's tale also involves a cauldron, but more frequently, the motif seems to be associated with eating (parts of a) snake, e.g., in the Icelandic Volsunga Saga (late 13th century), where Sigurd gained the knowledge of the speech of birds after tasting the heart of the serpent (dragon) Fafnir.
[4] The story that Taliesin's stanzas were clear whereas the king's bards made only nonsensical sounds may actually have a basis in linguistics, as Brythonic grammar underwent substantial changes during this period, marked by the loss of unvoiced final syllables (i.e., most Indo-European inflectional morphology) and the grammaticalization of consonant mutation.