I started up a game on Unltra-Violence, level hopped to E1M8 (IDCLEV18), and jumped in with a pistol. I got my ass handed to me, especially at first. You start looking at the backs of an imp and a soldier (shotgunner? can't remember) and as soon as you start shooting, enemies begin teleporting in right beside you (shotgunners and pinkies). Oh and there's a crack on the ground that radiates death if you step on it. After a few tries I made it a bit further, but it's going to take some trial and error and learning the map if I'm going to do it on Ultra-Violence.