Ooh, that does have potential. Right! Anyone targeted by a Wallmaster will notice that their shadow is growing larger, no matter how fast they move. They'll only stop tracking your movements just before they drop, so you do have about half a second to get out of range. Then, of course, you have a pissed off disembodied hand after you... but evade them long enough and they'll return to their place on the ceiling. Of course, if you don't move during that half second, you will get grabbed.