The Faceless One from Mike Mearls' "The Three Faces of Evil" was a heavy duty player from almost the beginning. He appears as an important cult leader in the adventure as written - definitely a major player, at least on the local scene; he would prove to be relatively small in the ultimate scheme of things for Age of Worms AP, but he made the perfect kind of second rank commander for my campaign. While a small cabal of fiendish and fiend-blooded foes topped the conspiracy for my campaign, this guy made himself felt in a much more material way.
As envisioned by Mearls, he was a bizarre and ruthless villain. I imagine his appearance was warped through the vile beings he consorted with or maybe he was some kind of alien. Between his appearance, lair (a magicked maze), and his kenku (murderous crow men) cultist followers, I knew he would be memorable even in the context of the one adventure. However, I knew The Faceless One could be so much more.
There was no shortage of skullduggery in this campaign - clashes with bloodthirsty cultists, kidnappings, etc. Whenever the players gathered information during their investigations, The Faceless One became a recurring name. While they never got to meet him face to face (sorry, I couldn't help myself) until they penetrated his secret lair, they felt a dreaded familiarity with him - physically and psychologically.
His kenku killers provided a great connection, serving as a corporate recurring villain in many ways. They seemed to show up as tangent adversaries (or simply observers) in encounters with other groups of villains. It got to be that their appearance indicated deeper secrets to the obvious drivers of the games (ie. "stop the bandits, stop the orcish warbands, etc.). What's more, they kenku also disposed of weak-linked allies. By the time the player characters met The Faceless One, they knew what kind of villain he was. The formula was simple - take every other adventure and just add kenku. OK, I kind of kid you a bit there - the decisions to insert kenku felt very organic; they showed up whenever The Faceless One needed something done in secret.
He was a tough encounter. He destroyed a brave/foolhardy dwarven warrior with a point-blank lightning bolt in a final showdown that also saw the end of another brave hero - and his lair was nothing short of a nightmare of ambushes and mad spirits. However, I think the sessions leading up to his demise did as much to build up this foe in the gamers' minds as the bloodbath they witnessed that evening.
The end of The Faceless One wasn't the end of the campaign, but he was a great milestone. In fact, he would have proved more than adequate for a complete story arc if I had decided to move onto other adventure objectives and foes altogether.