Star Wars: 10 Awesome Ideas Disney Must Include In Episode X
9. The Threat Of The Yuuzhan Vong
In Star Wars Legends the main threat Luke, Leia, and Han had to face after the destruction of the Empire was the Yuuzhan Vong. The Vong were a species of humanoid creatures from the Unknown Regions, hellbent on the destruction of others, with a hatred for machine technology, and a love of all things painful.
Legends lore has it that they left their own galaxy many millennia ago, and became nomadic space marauders. Think of them as a cross between the bugs from Starship Troopers and the Mongols hordes from our own history.
Obviously with the death of Luke, Leia and Han the existing Legends material is mostly defunct. But the basic plot of these guys invading the galaxy would make for one hell of an interesting story. What's most interesting is these villains are undetectable by the Force and are less susceptible to its power.
The whole Jedi vs Sith thing has been done to death at this point; with an enemy who could be a threat to both parties, we might see Dark and Light Sides Force-uses putting aside their differences (at least temporally) to fight an even greater foe.