The best thing Sigma managed to do was to dissipate the mist a bit around him by spinning his daggers around. At the same time, he used Rage and Vital Aura to boost his defenses a bit. However, his health was falling faster than Regeneration could help him. He had to make that skill level up faster in the future...
"Feiria isn't using her death knights, and she probably thinks that it would be too dangerous to keep using them against me…" Sigma thought. "Regardless, I need to find a way out of this mess."
Although it was an area-of-effect spell, it was unlikely that Sigma would be able to cancel the damage caused by it just by waiting for the skills necessary for that to level up. The mist also could poison his whole body, and he didn't have the option to protect his face alone to fight it…