Thane Korth'azz is one of the Four Horsemen of Naxxramas. He holds the power of flame, being even able to call forth fiery meteors from the skies.
Korth'azz is a fallen dwarf paladin. There is speculation that he fell to the Scourge after Uther's death, as he might have been a leading member of the Knights of the Silver Hand. This is at least partially confirmed when Alexandros Mograine refers to Korth'azz as "one of Uther's men".
Korth'azz likely represents the "Pale Rider of Death", based on his light green color scheme.