I have recently taken up farming Marshwood and there's something I'm wondering about how the enemies die.

I noticed that certain ones, upon death, give like a smoke effect on or above the ground. I can't tell if it's because I actually killed them or I killed an enemy that they're linked to maybe? Are they perhaps linked to another enemy like skulls are to mages in PL's Mt. Fang campaign? Once you kill a mage in Fang, the skulls around her die emitting a red smoke effect. You get the xp from the skulls but not the kill.

I've only played Marshwood when 21 was cap to unlock all the map so I'm definitely not knowledgeable on it.