The Crystal Cave is Book One of Mary Stewart’s Arthurian saga, which comprises five books: the Merlin trilogy (The Crystal Cave (1970), The Hollow Hills (1973), The Last Enchantment (1979)), The Wicked Day (1983), and The Prince and the Pilgrim (1995).
The Roman Empire having withdrawn in 410 AD, post-Roman Britain enjoys a golden age of instability, violence, and invasion. Myrddin Emrys, the bastard son of Welsh Princess Niniane, will be known by many names, of which the most familiar to modern readers is Merlin.
A bastard is beneath notice and this particular undersized bastard is not interested in the usual boyish activities. He isn’t a stalwart warrior. Fortunate for Merlin, as he might otherwise not have survived his youth. His ambitious uncle Camlach is perfectly willing to clarify dynastic succession by pruning the family tree but for the moment, Merlin isn’t an obvious threat.