Taran Wanderer is the fourth book in the Chronicles of Prydain series by Lloyd Alexander.
Plot:
Taran, Assistant Pig-Keeper of Caer Dallben want to be a pig-keeper no longer, as he nears his manhood. He sets out on a quest with his faithful friend and companion Gurgi. And not just some quest, the most important quest anyone could ever go on. A quest to find out who he really is.