As people migrated between Brittany and Britain over the centuries, the Celtic culture and legends merged. Much of that can still be perceived in Brittany nowadays, most notably in the Arthurian legendary forest Brocéliande, in whose waters the Lady Viviane raised Lancelot and where Morgan le Fay trapped her lovers in The Valley of No Return. This mysterious forest is still a great source of inspiration, for example its simulacrum Brokilon in The Witcher series.

Broceliande! in the perilous beauty of silence and menacing shade,
Thou art set on the shores of the sea down the haze
of horizons untravelled, unscanned.
Untroubled, untouched with the woes of this world
are the moon-marshalled hosts that invade

Only at dusk, when lavender clouds in the orient twilight disband,
Vanishing where all the blue afternoon they have drifted in solemn parade,
Sometimes a whisper comes down on the wind from the valleys of Fairyland —-

Sometimes an echo most mournful and faint like the horn of a huntsman strayed,
Faint and forlorn, half drowned in the murmur of foliage fitfully fanned,
Breathes in a burden of nameless regret till I startle,
disturbed and affrayed:

~Alan Seeger~