I can see the quest info for Dark Knight going a little like this:

Quest: "I Am The Knight"

Location: Outside Haukke Manor or butler from Haukke Manor in Old Gridania

Requirements: Level 30 Gladiator and Level 15 Marauder/Thaumaturge(?)

-There has been strange rumors of a knight clad in darkness wandering about the grounds of Haukke Manor and an adventurer is needed to investigate.