Goblin

Goblins are magical creatures however nothing else is known of them. According to dark future Chris Halliwell, the original Charmed Ones would face some goblins in the future, saying "It's gonna get ugly."

Book of Shadows

 * Goblins
 * Dark future Chris mentioned there being an entry in the Book of Shadows on Goblins. According to him it "Needs some serious updating".

Note

 * It can be presumed that Goblins are evil beings, because Chris told Piper that the Charmed Ones would end up going against some goblins in the future and it would get ugly.
 * Henry Mitchell Junior dressed up as goblin in the Destined episode "Halloweentown". He was transformed into a real goblin when the demon Ignatius cast a spell on the patrons of P3 on Halloween.