First mentioned/appeared in chapter 349 when Mechanical Slayer used it against Magistrate Weissman
Death's Sigh is a Tier 4 Skill [1]
Description[]
Since Shi Feng was able to fully negate Death's Sigh's damage using Fantasy World it can be assumed that Death's Sigh is a Tier 4 skill which deals magic damage.
"The Mechanical Slayer's body suddenly turned crimson, shrinking by half. The serrated greatsword also transformed into a blood-red scythe. A pitch-black aura of death surrounded the blade. Tightly gripping the scythe with both hands, the Slayer swung it at its surroundings.
Suddenly, black streaks of light shot out in all directions.
The black lights illuminated the surroundings for six full seconds, covering a range 200 yards in all directions. The area looked like it had been enclosed by a black dome. Everything within this dome was pitch-black, and nobody outside the dome could see anything within it.
After Death's Sigh ended, everything in the space was dead." [2]