I'm looking for a book I read in the 3rd grade, back in 2004. I'm 20 now so this was about 12 years ago and my memory of the book is a little hazy.
I recall the main plot of the story concerned a human boy abandoned by his parents and raised on another planet by an alien species. These aliens resembled something along the lines of a monkey/bear hybrid. They were very hairy and walked upright. One of these aliens acted as a mother to the boy.
These aliens had a mythology in which there existed a creature somewhat like Satan from Christian theology. This creature tempted people based on their deepest desires, but eventually "took their souls". If I remember correctly, the aliens never spoke the name of this creature. There was a forest that these aliens were wary of and it was warned that this evil creature lived in the forest.
Eventually, the human boy sets outs on a journey, either one of self discovery or to find his lost father, though I cannot remember which. Throughout his journey, he encounters some sort of large domed cities and a robotic waste disposal system that I believe almost kills him.
He encounters his father, who if I remember correctly is now some sort of mercenary or space pirate. One of his crew-members has a metal mechanical jaw. At some point towards the end of the story, the boy is becoming hopeless and actually encounters the evil creature and in his desperation almost succumbs to it.
The writing style is somewhat similar to Larklight by Philip Reeve. That's all I can remember. Any help is greatly appreciated.