In Celtic mythology the cauldron is indeed a magickal item.

Cauldrons have long been associated with wisdom, knowledge, life, death, wealth, and health, to name a few associations.

The cauldron is a symbol of the womb of the Goddess and is associated with the process of transformation.
The things which are made within the cauldron are imbued with magical properties.

This story tells of the birth of Taliesin. Cerridwen lived during the Arthurian times. She had an ugly son named Afagddu. Afagddu was not going to amount to anything due to his looks, but was not exactly excelling in wit and wisdom either. She consulted her spell books and found the spell for the cauldron of inspiration. She gathered all the ingredients and mixed them into the cauldron. She set it to boil for a year and a day, instructing her servant Gwion Bach to tend to it. Every day he tended the cauldron until one day at the end of the year, three drops splashed on his fingers.
All the inspiration meant for Afagddu was in those drops. Gwion sucked his fingers to cool them, and immediately knew past, present, and future. As the cauldron cracked behind him, he ran away with Cerridwen in pursuit
. As Gwion shape-shifted into a hare, Cerridwen became a hound and followed him even closer. He turned into a dove when she became an otter. She became a hawk and folowed him still. At last, he became a grain of wheat in a pile of wheat. She became a black hen and hunted through the wheat until she found the grain she sought. She found the grain that was Gwion and swallowed him. Shortly after, she gave birth to a son. He was too beautiful to kill outright. She cast him, bound in a bag, into the sea, where he was found by Elphin. In the words of the poet Taliesin as he emerged from the bag,

I have been a blue salmon,
a dog, a stag, a roebuck on the mountain
a stock, a spade, an axe in the hand
a buck, a bull, a stallion
upon a hill I was grown as grain
reaped and in the oven thrown
out of that roasting I fell to the ground
pecked up and swallowed by the black hen
in her crop nine nights lain
I have been dead, I have been alive, I am Taliesin.

The story of Bran the Blessed is told in the second branch of the Mabinogi. He gives his sister Branwen and a magic cauldron to the king of Ireland. When she is subsequently mistreated, word reaches Bran, who then wades across the Irish Sea to rescue her. The army of the Men of Britain sail next to him in ships.The final battle does not go well for the Welsh since the cauldron has the power to rejuvenate the slain warriors. The Britons prevail when one of the warriors manages to get into the cauldron and smash it by stretching to his full length.

I draw my knowledge from the famous cauldron,
The breath of nine muses keeps it boiling.
Is not the head of Annwn's cauldron so shaped:
Ridged with enamel, rimmed with pearl?
It will not boil the cowardly traitor's portion.

My own cauldron, cauldron of warming,
God-given from the mysterious elements;
ennobled is each belly from
which pours forth the oral utterance.
Amairgin White-knee am I,
blue tattooed shank and beard of grey.
My cauldron of warming serves up
multiplicity of forms
and many-coloured verse.
Not equally does God distribute
gifts to each person:
but some inclined, some prone, some supine,
some empty, some half-full,
some full of knowledge like Eber and Donn,
creating their verse
with innumerable chantings,
in masculine, feminine, and neuter,
in signs denoting double consonants,
long vowels and short vowels;
thus is its function metrically declared,
by the votary of this cauldron.
I sing of the cauldron of knowledge,
whench the law of each art is dispensed,
which gives boundless treasure,
which magnifies each artist in general
which gives each person its gift.