An Abyssal Duke is a level 62 elite elemental summoned from the Wind Stones around the various Twilight's Hammer camps in Silithus. The player must wear the Twilight Trappings and a when interacting with a wind stone to summon one (failure to wear it can lead to shocking results!). The elemental that is summoned is random, but there are items that can force a certain type to appear.
The Abyssal Dukes are:
Abyssal Dukes are tuned for a 5 person group, although it is possible for a level 70 player to solo one.