Mordant Grimsby is a level 42 quest giver located at Swamplight Manor deep in the the Quagmire in Dustwallow Marsh.

He starts the following quests:

•  [36] What's Haunting Witch Hill?
•  [36] The Witch's Bane
•  [36] Cleansing Witch Hill

See List of Dustwallow Marsh NPCs.