One of my champions has the coal stones ability (which is awesome!)  I have used it in many circumstances, but this one time, against a batch of ogres it glitched pretty bad.  After the cast animation, the game stalled for approx one minute before I clicked on the autoplay button which unstuck the game (the impact animation played) and the lighting for all the characters went out.

The rest of the battle looked like this.  (There was a little more light from the opposite direction).

I was not able to reproduce the effect from the save,.