Goblins are mischevious creatures. A group of them stole Skulduggery Pleasant's skull when he was meditating. Skulduggery said that goblins love gold, but prefer eating babies.
Goblins have only appeared in "Gold, Babies And The Brothers Muldoon".
However, the Muldoons were turned into goblins by Skulduggery Pleasant, and only collect gold because it helps them become human again.