Heat barrier

Rock and cinders crunched beneath his heavy tread, while the hazy air swirled at his passing. War squinted against the stinging fumes and blistering heat, so intense it would have proved a tangible barrier for most beings, and once more studied the domain of his so called lords and masters.
It was always the air that hit him first, the searing sulfur stench of things burning that should never have been able to burn; of gritty soot; of toxins that partook of an almost sentient joy in the ravages they caused, and were best avoided by any sane creature.

(...)

For wearing leagues, the Horseman trudged. Eventually, a faint sheen of sweat broke out across his normally impassive brow. He cursed the Charred Council silently, internally, but would not offer the satisfaction even of wiping the perspiration from his forehead.

***

The Abomination Vault, Chapter 4