force bolt would have that effect. I got killed by a hail of bones a few times.
One thing that I noticed that until imps as fighting units are nerfed someone could even win the game with only one imp armed with a bow and arrow.
I was shot by a imp. Happened about 2 times so far.
I noticed in the last fortress I uploaded my imps appear to be able to shoot 5 arrows in the time it takes for me to step into their line of fire.