When you controlled levelport to level 0, Nowhere, monsters that normally follow you through a levelport will do the same here (because they don’t know where you’re going). This will kill all of them and make them cease to exist, the same as you, but you can survive as usual with an amulet of life saving. This effectively allows you to controlled levelport to 0 to dispose of any monsters that would follow you.

Note: because it depends on levelporting to level 0, it won’t work when carrying the Amulet or in the End Game.