Storm

You may designate 5 adjacent hexes on the world map to temporarily become "Storm hexes". For every 5 the caster exceeds the DC, add another Storm hex. When a battle begins within a Storm hex created by this spell, designate tiles equal to the amount of connected Storm hexes on the world map, outside of enemy territory, to become Hazardous terrain. Casting Storm while in another nation's territory raises the Complexity of the spell by one tier. Additionally, by increasing the cost of this spell by 3, you can grant immunity to damage from the Storm to all domestic units.