A hole in the basement opens up, and a shambling corpse possessed by hungry ghosts stumbles through. When it reaches the target - or if it's stopped from doing so - those ghosts come screaming out, blown before a silent wind, to drag the victim irresistibly back down into nowhere at all. As they do, it becomes horribly, unavoidably clear that few of the ghosts were ever human.
Or maybe the angles of the room collapse, perspective and geometry enslaved by the will of something from a place where neither exist, and the target is sliced to pieces by Escher-esque shifting lines and curves before at last reality re-imposes itself, leaving impossible bloodstains spattered across the far corner, the edge of a table, the branches of a tree visible outside the window...
Or perhaps the target is speaking with friends (or even characters) when a plethora of twisted, eager appendages of all description burst impossibly from every orifice, sink nails and claws and burrowing tentacles into his flesh, and then constrict - pulling the target in on herself, imploding her into nothing at all.
A storm that makes no sound, whose unholy lightning strikes shine with irradiated green light. A gibbering abomination waiting in the closet, with too many limbs tipped with too many keratinous scythes. A beast composed of nothing but pale gray fire and thousands of oversized, serrated teeth. The backwards world inside the mirror, tarnishing black and inhabited by laughing rats with the voices and hands of children, who sing a song that wears away the boundaries between here and there - when they finish the last verse, there will be no difference, and the wretch forced to listen will be trapped with them forever inside the next mirror he sees.
