The sight of the smoke alone was overwhelming.
Evan wasn't affected at all thanks to his temporary sphere shield. Spirits were invulnerable to such things, of course, but his Guardians — as well as Ardyn — weren't so lucky.
He had read about this ability before. It was said in the books that the Calamity had several tricks up its sleeve whenever it felt that it was in danger. There were a number of abilities listed, and it included this dangerous thick fog.
This black smoke was said to be a deadly smog that essentially paralyzed and eventually killed those who inhaled it for too long. In some cases, if not death, the victim would experience their worst fears as the smog invaded their head and all of their senses.
Fortunately, Summoners were immune to such things, as their holy light repelled dark magic and evil auras through the intricate sealing process.