Ghost BrothersG 10

This achievement unlocks after completing two quests: "Bored to Deah" and "Gone, but not Forgotten" from the ghost brothers Sam and Max (which you may remember from Fable 2 as they mention a mantis in Bloodstone).
Both of these quests are located in the Morningwood cementary, but are available only after your first meeting with Page in Bowerstone Old Quarter.

First quest from the brothers will have you go to Millfields, where you must find and dig out the Normanomicon from a grave and then fight a few waves of hollow men.

The second quest should be available from Sam shortly after the first one has been completed. Sam will have you following Max into a new sub-area, the Reliquary. Follow Max until the final area, where you will fight waves of both ghosts and hollow men. After an in-game cutscene, the achievement should unlock on the quest completion page.