The Advent invaded my system with a large fleet and tried to take my planet. Fortunately for me, I had a fleet sitting right there, in addition to tons of defenses.

Anyways, right in the middle of the battle, this very large "black hole" effect pops up, pretty much right in the middle of the advent forces, pretty much completely engulfing the entire advent fleet. It stayed for a long time - the entire battle. I think it flickd off one or two times, but came right back quick. It was spherical in shape, and had lights and tracers going off inside of it.

What was it?