Idea for a necromancy spell:

Cull the Herd
5 mana resistance
18 Inches
When a necromancer spots a unit turning tail, he knows that the time is ripe to reap those whose Wills are broken. Corrupting the winds of magic around the hapless victims, he multiplies their fear tenfold, that men literally die of terror in their armour or fall upon their swords fearing the entities that swirl above them brought about the necromancers foul spell.

This spell may only be cast upon an enemy unit that is broken. It must be within range and line of sight of the caster. Once cast, the unit must immediately make a soldiering check. If it passes, it takes damage equal to the number of successes you rolled. If the unit fails, you roll a d6 for each success rolled and cause that much damage to the unit.