The backstory: On long boats, the Order of Iron came to the Isles. They killed the Fell Queen, Eil, and pulled her tower to the ground. They slew the monsters and sealed the Underworld. The people embraced the Order of Iron and forgot the Old Ways.
Five years have passed. On the rubble of Eil's tower, the Iron Citadel now stands. People pray to the Ironite's god. Magic is outlawed, as it caused the Bleak Times.
Rumors abound that the monsters weren't all slain... and the ones that remain hide in the wilderness or behind the faces of your neighbors. Are the players agents of Order, rooting out monsters and witches? Are they heretics, seeking to bring back the Old Ways? Are they simply feckless sellswords who seek to claim whatever treasures haven't ended up in the Order's vaults?
Rules : B/X D&D + JB's "Complete B/X Adventurer"
Classes Permitted: B/X Rules: Cleric, Fighter, Thief
Complete B/X Adventurer: Witch-Hunter (Also Barbarian, Bard, Gnome, Mystic, and Ogre-Kin if running a game outside the Order)
Flavor/Visual Reference: Blood Omen: Legacy of Kain (90's video game), Dark Souls (video game), The Crucible (either the original play or the film), Warhammer Fantasy Roleplay 1st Edition
"But Wait, I Don't Own CB/XA"
Apply the class fixes in my previous post. You can fold Witch-Hunters into clerics, or just let clerics use any weapon, or just have a class that fights and saves as a fighter and can use all the Detect/Protect type spells, but requires % more xp to level.