New dark spell

A new dark spell made of dark elixer that can stain a certain range to reveal traps and the remaining health of buildings for some time!

upgrade to increase its radius and duration

lvl1;duration 20 sec, range 6 tiles
lvl2 ;duration 25 sec, range 8 tiles
lvl3; duration 30 sec range 10 tiles

And.. who would use this spell? I know I wouldn't. I mean, I can assume the position of the traps, but I'd for sure not waste a spell slot to prove myself a giant bomb was there.