Ridiculous D&D contrivances

[KazilDarkeye]

HOW DOES IT FIND YOU?!

Quite a good morsel, but not filling enough.

Seriously though - according to Lords of Madness:
1) It can hear you, it just doesn't have recognisable ears (similar to how insects hear without having ears. According to the book the whole membrane (the surface of the "brain") functions as a giant ear.
2) They also possess a sense of electroreception similar to that used by sharks and rays.

3) The flight effect is a magical effect similar to a Ravid's or Beholder's.

Thus, they have blindsense that's actually pretty annoying to disable, because you have to use two countermeasures instead of just one.