Some creatures inspire fear as is indicated in their relevant Army book and these include large and disturbing monsters such as Trolls, as well as supernatural horrors such as Skeletons. A unit must take a Fear test if it is faced by one of the following situations:
If charged by a Fear-causing enemy.
If a unit wishes to charge a Fear-causing enemy.
Charged by Fear-causing Enemies
If a Fear-causing enemy unit declares a charge against it, a unit must take a test to see if it can overcome that fear and take the charge. First declare the unit's intended charge reaction, then test as soon as the Fear-causing unit is determined to be within charge range.
If the test is passed, the unit can react to the charge as normal.
If the unit fails its test and its unit strength is lower than the unit strength of the Fear-causing charging enemy unit, the unit must immediately change its charge reaction to 'flee
If the unit fails its test but its unit strength is equal to or higher than the unit strength of the Fear-causing charging enemy unit, it will fight on as normal but must roll 6s to score hits in the first turn of close combat against the Fear-causing enemy models (no modifiers or special rules apply - only by rolling an unmodified 6 can models score hits against these enemies).
If more than one Fear-causing unit is declaring charges against it, a unit must take each test separately.
Wishing to Declare a Charge Against a Fear-causing Enemy
If a unit wishes to declare a charge against an enemy that causes Fear, it must take a test to overcome its fear first. If the unit is unfortunate and the test is failed, it may not charge and must remain stationary in that movement phase, and for the rest of the turn is treated in the same way as a unit that has failed a charge.
If the test is passed, the unit may declare the charge as normal.