Was messing around today with directional spells and a mirror. Lightning and Fireball both did about 60-70 points of damage. Cone of Cold did about 40-50. Magic Missile did 25. I then decided to try Phantasmal Forces, and it said:
In What Direction? The spell caster (thats you) believed!
I also suffered 42 damage the first time and 53 the second time.
Teleport Away didn't work on the mirror.
Those were the only directional spells I had at the time. Would be interesting to try a Scroll of Pulverization. :)