The below description is taken from LEGO.com.
Oops, did you step on something? Hee hee hee!
The Goblin is a mischievous little imp of the forest. He scampers through the shadows and hides out in rocky caves and hollow trees, snatching up bugs and birds’ eggs for his supper…and wherever he goes, he’s always giggling to himself about all of the tricks that he’s going to play.
Have you ever been building something and thought that a brick was missing, only to discover it later sitting right there on the table? That was the Goblin’s doing. Inside his magical bag, he keeps all of the pieces that people think they’ve misplaced, and he loves to leave them just where you don’t expect to find them – like under your feet!