Celtika

Merlin is almost young, and immortal, one of those born to walk the paths of the world, a man with charm carved into his bones, and enchantment running through his body thicker than blood . . .
And this is a time of heroes, centuries before King Arthur is born, men and women who, though not gods themselves, are something more than mere mortals. For decades, Jason has been immured in his ship Argo in a lake in the far north, alive, but not, still traumatised by the murder of his sons by his enchantress wife Medea . . . until Merlin sees through the veil of enchantment and realises the boys were never killed; it was all a trick.
Through the mists-shrouded isle of Alba to Greek Land, Merlin leads Jason and his Argonauts, some old, some new, on a quest to find the boys, journey filled with heroism and heartbreak, truth and treachery.