Commander Samaul is a level 40 quest giver located in Foothold Citadel on Theramore Isle in the contested territory of Dustwallow Marsh.
He starts the quest 
[35] The Missing Diplomat (14).
See List of Dustwallow Marsh NPCs.
Trivia[]
Commander Samaul, along with Captain Garran Vimes, is probably a reference to Commander (formerly Captain) Samuel Vimes of the Ankh-Morpork City Guard, in the popular Discworld series of novels.