In many battles to date, I destroy a troop only for it to remain on the battlefield. However, the game does not pay attention to the dead troop and when you do skull damage, it goes to the next troop. Also, if you eliminate the other troops, you still get the win. It is as if the dead troop acts as a ghost troop.
It’s been popping up in battles during Pet Recue, Explore, and Challenge.
I use Dragon Soul During Challenges (Explode spell). (Farming souls to bring the dawn.)
I use Gorgotha for the other two (Explode spell again) and Infernus (another exploder).
Both spells explode random gems therefore can’t say if blazing skulls were involved.
It never occurred when I was using Artema for my mana generator come to think of it.