So, today I tried out a hunch of mine regarding this elusive little component in the Plasma Plugin. Unleash Satan. So...what does it do exactly? Well it's present in Laki for one.
If you take a look at the ground in Laki, you'll notice that it's vertex colored so that underneath the waveset is a nice serene light blue. But see, if you just vertex color a place like that, and then add in the lights for a day night cycle, no matter how you set it up the vertex colors will be whitewashed by the overpowering of the lights affects on the land. The vertex colors will be either really dull or fade out into nothing depending on the shade of them. So to both preserve the lights affects on the land, as well as the vertex coloring, you use Unleash Satan and attach it to the land. Presto. Mystery solved. Unleash Satan was apparently a hack by someone at Cyan to get around some rendering problems they were having with ages like Laki.