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A strange organism in many ways. They are like bodiless minds, but incapable of thought. Normally, they cannot be seen. They can be faintly heard, with a sound like a swarm of flies, and animals can certainly sense them. They are parasitic; they take over the mind and body of other creatures. Hivers normally target powerful creatures, like tigers, and when attacking Humans, Wizards and kings. The people and things a hiver consumes begin to become incredibly powerful, eventually dying insane. The reason why they do this seems to be because they're afraid of the whole universe. They are completely and utterly aware of everything around them, knowing every single blade of grass, seeing all the colours in a tree. They envy humans because, in comparison, we are nearly blind, with the amazing talent known as 'boredom'.

Annotation

In Alan Garner's fantasy novel, The Moon of Gomrath (1962), there is a sentient being, taking the native form of a nebuluous black cloud with two glowing crimson eyes, which will possess and inhabit the body of any living creature until that creature dies under the intensity of the spirit posessing it. This creature then looks for another host, and carries on serially possessing living creatures. This may be a version of an old Celtic spirit of evil, rather than something invented by Garner.

Garner's "Brollochan" is to all other intents and purposes identical with the Hiver, in purpose, practice and result. (Although the souls of the Brollochan's victims are forced into Anbarn, the Celtic hell: with the Hiver, some shreds of sentience and independence live on) The only things that defeat the Brollochan are the witches - an altogether darker and more malevolent creation in Garner's world - and the Elves, who have more in common with Tolkein's vision than Pratchett's (although Elves in Garner's world are dwarf-sized). In a Celtic exorcism, the Brollachan is forced from the body of Susan (heroine and in all but name, an apprentice white witch) and the noise is like that of thousands of flies...

Perhaps TP read Garner in his childhood and this is an unconscious borrowing: or like Garner, he has gone back to the same root sources in Celtic myth, which explain the similarities between the two creations? As TP himself put it, when the ignorant accused him of plagiarising JK Rowling: "Look, we're all fishing from the same stream here!"