Delayed Blast Fireball

Caster Level(s): Wizard / Sorcerer 7
Innate Level: 7
School: Evocation
Descriptor(s): Fire
Component(s): Verbal, Somatic
Range: Medium
Area of Effect / Target: Huge
Duration: 1 Round / 3 Levels
Additional Counter Spells:
Save: Reflex 1/2
Spell Resistance: Yes

The caster creates a small, magical zone that can detect the passage of enemy creatures. When the field is activated, it explodes, doing 1d6 points of fire damage per caster level to all within the area of effect up to level 20, plus an additional 1d6 points per 2 caster levels thereafter.