My theory is that the final universe that Twilight and Starlight visit in the end of season 6 that was a barren wasteland was caused by this little Grey Knight that took a wrong turn out of the warp. He used his nemesis force weapons and Matt Ward sanctioned Mary Sueness to purge the witch and alien.
Either that or it was a little parasprite that got too hungry. What do you think caused that wasteland universe?