Usniel, the Lord of the Deeps. 
Usniel is the guardian of the great serpents, whose own tails reach into the very roots of the Realm of Ghyran, He dwells deep in the ocean in a reefcastle and cannot enter the shallows or the surface world, needing the pressure to survive. 
An ancient being, he is arbiter of and voice for the serpents whose slow, cyclopean motions move the very waters of the world above. At the beginning of the Age of Sigmar he discovered a Chaos taint deep in his realm, battling it secretly. 
|Nothing from above can overcome us. This is not their realm, and never will be
. ~Usniel to Kelara.