"That was no ordinary creature back there; it was an ancient earth golem from the deep"-Hunter
The Golem of the Deep is a lava-based creature originating from the Burned lands, the volcanic wasteland 10 miles west of Warfang. It is novelized in several books, and appears during nearly all sieges of the city.
In all of it's novelizations, it is first encountered in the Catacombs beneath the Mountain of Malefor, where it attempts to kill the main characters, Hunter, Spiril, and Cynder, seeming, in later novels, to deliberately attack Cynder, and in some cases ignoring other characters around her.
"It's in the earth beneath us! all of you, run, run!"-Cynder
In it's secondary encounters, the golem bores under the city's walls, wreaking havoc and destroying large portions of the city. He is generally always confronted by the High Council, but when they are defeated, which inevitably happens in all the novels except one, where he is killed by a collapsing building. He has to face both dragons, and while assaulting the Fortress, he is killed by the two young dragons before falling dead to the streets below.