Who is Bodachs from Brother Odd and what is their importance?

Bodachs is a supernatural entity seen only by Odd Thomas and Boo, the Abbey's only dog. Bodachs are inky black and have little more substance than the shadows themselves. They slink along, low to the ground, as large as an average man. Suggestive of something that resembles a wolf, Bodachs are sleek, sinister and featureless. Though Bodachs are actually part of the folklore of the British Isles and are supposed to be vile beasts that slither down chimneys and steal children that misbehave, they are as close to describing what Odd sees as he can get.