I got one one of these as a kill task at level 14 and spent ages looking for them. If you go to Caer Ulfwych and head out the back in a south-ish direction you'll run across a sylvan goblin camp (Loc: 34k 44k). A sylvan goblin magician spawns in the camp and was green to me at 14.
Stumbled into one of these and made him my pet, what a blast and I mean literally...
To test him out I targetted an easy blue mob, the mage nukes it 3 times while its running towards us and it dies at his feet. I loved it. After a couple hours as a pet he began to get buggy...kept standing still not following and constantly re buffing himself.