The Endless Void is the result of one trying to use their stream to open up a rift of madness. It drives even the most sane people into a state of madness, hearing their own stream on the other side, hearing it all over, and hearing noises all over the place.
Thou who opens up the void must be prepared for endless madness. Nothing is on the other side: Just emptiness and madness. No sanity lives in here.
tl;dr Endless music/sound effects all over the place and even opening up your stream and looking at the stream within the stream within the stream etc etc etc.