Blades of Wind

A spell so powerful it is only used by the god of the winds. The caster chooses a 100 ft square in which the wind compresses and moves with such force that it can cut steel. Every turn it is activated, all creatures within the 100 foot square are dealt 5d12 force, and 2d20 slashing damage. The winds do not affect the caster, and they last until the caster breaks concentration.