I have installed 0.37.0.12730 version of the game.
This effect occurs in many different locations, but not regularly. So when I wanted to look closely today, he disappeared for half a day))).
And I already thought that maybe for good, but then a few times it did meet again.
I can not say exactly what spell causes this effect, but I always use the bunch of spells that is visible in the bottom picture.
Playing as a character of other classes I never observed anything like that.
Although playing as an assassin using the same scheme as the necromancer - the creation and simultaneous elimination of a large number of purple chips.
I do not know how else to help in catching this bug, but if I notice something new, I will definitely write here.