Ok, time for one more version of this spell.

SPHERE OF DEPRESSION M4

School enchantment

Casting Time 1 standard action

Range close (25 ft. + 5 ft./level)

Duration 1 round/level (D)

Saving Throw Will; Spell Resistance yes

You summon forth a five foot sphere of blue light to a point in range. The sphere radiates an area of faint blue light to to 20 feet that drains the will to live of any creature in it.. All creatures that enter the area of the blue light must make a Will saving throw.  A creature that succeeds at the saving throw is only fatigued, unless it is already fatigued, in which case it instead becomes exhausted despite the saving throw. Creatures that fail the save are instead are exhausted. If a creature leave the area of blue light, the conditions from the sphere ends. As a swift action, each turn you can move the sphere up to 30 feet.

Thoughts?