Each can happen independently:

Billy Corgan (w/shaved head) - His huge bald head erupts and out pops an alien space creature to do damage to Reznor and Manson.

Marilyn Manson - conjures up the spirits of the dead. Wherein the ghost of Tupac Shakur and Biggie Smalls proceed to bust caps in the respective asses of both Corgan and Reznor.

Trent Reznor - (w/ his fetish bent) ( e.g. leather wardrobe, Closer video, et. al.) - used chains and whips to beat Corgan and Marilyn into submission. He proceeds to restrain them, whereupon he calls out, "the gimp" who proceeds to anally rape the two musicians. The gimp reveals himself to be Rob Halford of Judas Priest. Rob proceeds to go medieval on Reznor as well and proclaim himself a "bad muthafaka"