The final story elements for my campaign in terms of villains are going to be an infamous 'Red Wizard' from the first game we played in this setting (the only major villain to survive the PC's) and a White Dracolich whom they had defeated, but not destroyed.
The 'Red Wizard' is known to the PC's by his crimson robes, his powerful spell-casting, and his callous use of minions. He rarely even seems to know their names. The 'Red Wizard' is known to have some sort of pact with evil outsiders and to be bent on locating and killing all Fireblood Dwarves in the setting.
He is vain (wants to kill Fireblood Dwarves for their hair color matching his), overconfident (rarely checks to see if his minions or his plots have succeeded), lazy (his apprentice prepares most of his scrolls), and extremely wasteful of minions.
The 'Red Wizard' aquires minions through domination magic mostly, but is not above the occasional bribe.
Once he wipes out the Fireblood Dwarves, the 'Red Wizard' plans to use their deaths to trigger an evil magical event and increase his power. Then he plans to travel to a parallel plane of psionic magic and wipe out the psions for killing his brother centuries ago. The 'Red Wizard' is in no rush.
The White Dracolich is a powerful white dragon Dread Necromancer who recently escaped his imprisonment (by an old adventuring party) and is now re-consolidating his rule over Frostfell, the frozen continent to the north. Two of his descendants control much of the territory and have already joined up with him. They are female identical twin great wyrm white dragons. Other minions include frost giants, a scattering of lesser white dragons, frost orcs, and a moderately powerful frost mage.
The initial encounters for the White Dracolich plotline will probably be 'scouting missions' from Frostfell to the continent of Khorvaire by his minions. These may involve a frost orc raiding party on a longship or possibly flyovers by some of the lesser white dragons.
I intend these two villains for higher levels of play while the lower levels focus on the goblins/eyeless/black dragon occupying force in the PC's homeland and on the drow from the shadow plane intent on capturing and consuming the PC's starmetal weapons and armor (and on the case of the two warforged consuming the PC's).
What I am currently debating is whether or not to put the 'Red Mage' behind the drow attacks. He is hitting middle age, even for an elf, and since he is vain, might find a variant on the Green Star Adept prestige class to be a viable method to achieve immortality and preserve his 'looks'.