Goblins

Goblins are hideous humanoid beings with piglike faces and batlike wings that like to terrorize other beings they come across with their magical powers. They are thought to live for hundreds of years in mythical folklore and are universally seen as creatures of bad luck.

Mystico was one such goblin that caused trouble for the Smurfs when they had awakened him.

In "The Goblin of Boulder Wood", Peewit was thought to be a goblin.

Second Smurfette Series
In The Second Smurfette series, Goblins play a miajor role in the series. The most popular Goblin would be Mystico, who continued from his cartoon show counterpart's history. Other goblins would be Mildew (Mystico's brother), Hazel and Destive.

In this series, Goblins are very proud creatures and are not allowed to interact with other creatures. Mystico was the first who dispobeyed this rule and this was what caused him to get traped in the fountain. Mildew and Destive, enhance this rule and are very strict about it. But Mildew loses intrest in this rule when he develops feelings for Tracer.

They reside in different locations in different forests, Mystico and co. call the one they reside in "Goblin Land", Destive is from a different location, whose name is unknown.