Arianrhod ferch Dôn is one of the great, unresolved figures of Welsh myth. Her name means 'silver wheel,' and the medieval Welsh used it for the Corona Borealis — the half-circle of stars that turns over the northern sky. Her fortress, Caer Arianrhod, was a real Iron Age earthwork on a low reef in Caernarfon Bay, a mile or so offshore from Dinas Dinlle on the Llŷn peninsula. At low spring tides, the reef can still be seen.
In the Fourth Branch of the Mabinogi, Math is seeking a new virgin foot-holder after Goewin's rape. Gwydion proposes his sister Arianrhod. To prove her chastity, she is asked to step over Math's wand. She does — and as she does, she gives birth on the spot to a sturdy boy, who runs for the sea, and to a 'small thing' that Gwydion catches up in a fold of silk and hides in a chest at the foot of his bed.
The sturdy boy is named Dylan ail Don and is lost to the sea forever. The small thing in the chest grows, in time, into a boy himself — and Arianrhod refuses to acknowledge him. When Gwydion finally presents the child to her at court, she lays three terrible geasa on him: he shall have no name unless she gives it to him; he shall have no arms unless she equips him; and he shall have no wife of any race that is now on this earth.
Gwydion, in three separate acts of trickery, breaks all three curses. The child becomes Lleu Llaw Gyffes. The wife, conjured from flowers because no human woman can be given, becomes Blodeuwedd. The rest of the Branch is the long, painful consequence of Arianrhod's refusal.
She is not a villain. She is something stranger and older. She is a goddess of stars and tides who has been forced into a hall full of men, asked to prove an impossible thing, publicly humiliated, and then asked to mother the result. Her curses are, among other things, the only power left to her in the room. The fortress out in the bay, slowly being eaten by the sea, fits her: a place that was once high above the waves and is now half-drowned, still there at low tide, still refusing to disappear.
Wear something inspired by Arianrhod and you wear the silver wheel of stars over the Llŷn coast — the goddess whose 'no' shaped the rest of the Mabinogi, and whose fortress is still out there in Caernarfon Bay if you know exactly where to look.