What is this skill?

I keep seeing this "smoke" for long time when fighting demons with players from my friends list, and wasn't able to figure out which hero produce it and what skill it is:

Anyone identify the skill?

Solution 1:

that's Gunslinger's Skill Trick Shot

some details of the Gunslinger's Skill (http://castle-clash.wikia.com/wiki/Gunslinger):

Skill Trick Shot:

Deals [160%~550%] ATK DMG to a random enemy target, and reduces received healing by [10%~100%] for 2s. Hero takes [15%~90%] less DMG for 2s, and summons a Warflyer for 12s. (Cooldown: 3s. This Hero gains 25 Energy every second.) The Warflyer's skill targets the enemy with the lowest HP percentage, inflicting Coma for 1s and dealing a total of 300% Warflyer ATK DMG to all enemy targets in that area. (Warflyer is Elusive and has Lv5 Scatter. In defense battles, Warflyer ignores Hero Base range.)