Books like The Black Cauldron

Taran, the Assistant Pig-Keeper, and his friends are led into a mortal struggle with Arawn and his deathless warriors. Taran must wrest the black cauldron from them, for it is the cauldron that gives them their evil strength. But can he withstand the three enchantresses, who are determined to turn him and his companions into toads? Taran has not foreseen the awful price he will have to pay in his defence of Prydain...