If there is one word that you have to associate with Mervyn Peake it is imagination and it is a feature of this story from the very outset.
Those who have read the Gormenghast Trilogy will be familiar with the figure of Titus Groan. The boy runs away from his inheritance and the castle his family rule over in those stories and heads into strange worlds. This story is apparently what happened to him in between deciding to run away and when he got to the wilderness.
What happens here involves a relatively small cast it appears but dark ideas that are described in such a way that they become even darker if that makes sense. The idea of a goat, hyena and lamb talking and living in relative seclusion is made much darker with the revelation that they were once men and have been destroyed by the lamb. He has encouraged them to resemble and grow to become beasts and presumably with the arrival in his lair of Titus will try to do so once again.
The way evil and fear are portrayed and inspired is through the description of colour, particularly of eyes, and of the eerie use of animals, with dogs being a feature, before Titus even comes across the goat and his friends.