Lugh

Lugh, God of Wit of The Tuatha De Danaan.
First appeared in Season 2.
Season 2
Lugh was one of the few who did not seem under Saint Patrick's spell when Fionn Corvin visited Tir Na Nog. He remained insolent and wry, though he didn't get involved in the rebellion in a hands-on kind of way.
He brought Fionn to face the Fomori so that Fionn could help him regain his steed.
Season 3
Arrived at Ford's Halloween party in an elaborate and intricate R2-D2 costume. His immobility and Ford's steps into the Bleak Hall necessitated he use his darkness powers to create a ramp into the house.