Character Analysis
A Brother and a Friend
Cadal is the first person Merlin can really talk to in Ambrosius' court. He's funny and chill and immediately takes to the pathetic little wizard. Merlin appreciates Cadal's acceptance:
I thought at first he might resent [being my servant] […] but he did not seem to mind, in fact I got the impression that he was pleased. He was soon on easy terms with me, and, since there were no other boys of my age about the place, he was my constant companion. (II.6.25)
It doesn't take long, of course, for Cadal to realize that Merlin will be a handful. Not only is the boy strong-willed and intelligent, but he also seems not to fear death. Too bad for Cadal that he does. But when Merlin bolts headlong toward the human sacrifice taking place on the isle of the druids, it's just not in him to abandon Merlin to an evil fate.
That doesn't mean he has to be happy about it—and it's not in Cadal's nature to keep his feelings back:
"High-handed little fool. Might have got yourself killed, meddling with that lot.. […] You should've heard what I was calling you, too. Proper little nuisance was the least of it." (III.11.34, 36)
After this hair-raising experience, Cadal grows more confident in Merlin's instincts, even if they run against his own. He understands that there's something special about this boy, and he understands that his own destiny is simply to follow. Well, and to keep the kid alive, too. Sometimes, those two directives are at odds:
I made for the door, but [Cadal] got there ahead of me, and paused with his hand on the latch. His eyes were scared. "You really mean leave you on your own in the middle of that wolf-pack?" (III.11.72)
Cadal earns a gold star for trusting Merlin's instincts enough to let him go. But you can bet he also scrounged up some escape horses, just in case his master needed an escape plan.
Witness to Weirdness
Cadal has to put up with a lot of supernatural weirdness from his master. It's a sign of his absolute loyalty to Merlin and Ambrosius that he doesn't pick up his skirts and head for the hills, really. Even Cadal himself jokes that no one in Vortigern's camp wants his job:
"When I said I was your servant, they couldn't shove me in here fast enough. Seems there isn't exactly a rush to look after sorcerers of your class." (III.11.9)
Cadal, in fact, has a terrifying front row seat when "the god" speaks through Merlin. He hits the nail on the head when he describes the experience:
"And you talk as if you were just a voice and not a person. […] Or as if you'd gone somewhere else and left your body for something else to speak through. Like a horn being blown through to make the sound carry…it frightens me." (II.11.70)
This type of possession might put just about anyone off—but Cadal's cool with it. He senses that Merlin's on the right track with everything he does, even when all the alarm bells are going off in Cadal's own head. When things look bad, as they do outside of Tintagel, Cadal has a kind of fatalistic acceptance of Merlin's "sight":
"Yes, I'd say you know what you're about. Which is just as well, Master Merlin, because otherwise, you realize, you're risking the life of the King of Britain for a night's lust?" (V.6.60)
He can't resist inserting a patronizing dig in there ("…you realize…"), but it's pretty clear that Cadal is going to stay put and wait for a sign from his master even if death comes—as it does—up the narrow path.
Servant of Destiny
Spoiler: Cadal won't be Merlin's servant in the next three books of the series. But Merlin's quick to point out to him that their extraordinary adventures together won't have been in vain; he's going to use everything that Cadal taught him in life to bring up the great King Arthur:
"[…] I shall take him out of the King's reach, and keep him and teach him all that Galapas taught me, and Ambrosius, and you, even Belasius. He will be the sum of all our lives, and when he is grown he will come back and be crowned King at Winchester." (V.10.68)
That may seem like cold comfort , but Cadal seems down with it. He's true to the end of his life, and Merlin rewards him by giving him a part in the most glorious legend the Western world will ever know. Not bad, really.
Cadal's Timeline