The Duke of Fathoms is one of the Elemental Nobles of the Abyssal Council. The Cenarion Circle believe that he and and the other three Dukes are the primary force behind the organization of the Twilight's Hammer Cultists in Silithus.
The Duke of Fathoms does not appear normally in the standard plane of existance but must be summoned. There are two ways of summoning the Duke:
- Aquire a set of Twilight Trappings and a
[Twilight Cultist Medallion of Station]. This will make you appear to be a middle-ranked leader of the Twilight's Hammer. Travel to a Wind stone and use it to summon a Duke. You have a 1 in 4 chance of summoning the Duke of Fathoms. - Turn in Encrypted Twilight Texts to Hermit Ortell. He will then mail you a random item. If you get a Scroll: Create Signet of Beckoning (Water), you can combine that with a
[Dark Rune] and 5 
[Enchanted Water] to create a [Signet of Beckoning: Water]. This signet can be used to specifically summon the Duke of Fathoms.
The Duke of Fathoms has a knockback attack that wipes aggro. The knockback is also quite strong and due to fast respawns of some mobs in the area, this might cause many adds to join the battle and quickly turn the tide against a party.
Ranged DPS is valuable, because all those in melee range will be affected by the knockback.