Dagun the Ravenous is a level 43 elite humanoid giant summoned in Dustwallow Marsh. Although Dagun appears to be a sea giant, he is classified as a humanoid.
Dagun can be summoned by using Enchanted Sea Kelp at the Seaworn Altar. Both Gerrig Bonegrip and Keeper Bel'dugur want the Hand of Dagun.
Drops [Hand of Dagun] for the quests:
Dagun is almost definitely a reference to the creature Dagon, described in H.P. Lovecraft's The Shadow Over Innsmouth as a being worshiped by the murloc-like Deep Ones.