The Night Spirit
The Night Spirit is an evil deity mentioned in the Ewoks cartoon series, which is loosely affiliated with the expanded Star Wars universe - although mentioned many times this creature has never been seen in the series and may well be a symbolic figure rather than a literal being: though some of the Night Spirit's followers have claimed to be visited by the entity, suggesting it may also be a sentient entity of some description.
Night Spirit is worshiped by the Duloks but feared by Ewoks and was said to have arrived on Endor in ancient times on a meteorite - ever since its arrival it has taken on the role of a personification of the dark side of the Force and seeks to ruin everything on Endor, presumably out of sheer malice.
As well as the Duloks other followers of Night Spirit that have survived are the witch Morag and the evil Stranger - both of whom were major antagonists towards the Ewoks and recurring enemies in the series.