The Fires of Merlin

Blurb

The Fires of Merlin is a 1998 fantasy novel by T. A. Barron published by Penguin. It is the third of The Lost Years of Merlin, a five-book series providing a childhood story for the legendary Merlin, wizard of Arthurian legend.
Wings of Fire, the once-sleeping dragon, now threatens Fincayra with his raging fury. Merlin, whose magical powers are new and unproven, is the only one who can stop him - though it could cost the young wizard his life.
Before facing the dragon's fires, Merlin must confront several others: the dreaded kreelixes, who live to devour magic; the mysterious Wheel of Wye; the sorceress Domnu, who holds the treasured Galator; and perhaps most importantly and most challenging, those fires within himself.