You use your brain to generate magical psychic energy, and you attack a creature's brain with it.  These "Brainwaves" are extra effective against weak-minded foes.  The creature must make a successful Intelligence Saving Throw or take (1d10) psychic damage.  If the creature's Intelligence Score is 5 or lower, then the spell deals an extra (1d6) psychic damage. 

At Higher Levels.  The spell deals (2d10) damage at the 5th level, (3d10) at the 11th level, (4d10) at the 17th level, and finally (5d10) at the 20th level.  The Intelligence score required for a creature to avoid an extra (1d6) psychic damage equals 7 at the 5th level, 9 at the 11th level, 11 at the 17th level, and 13 at the 20th level.