Some creatures are so large or disturbing that they provoke an irrational fear in the foe.
Source: Warhammer Fantasy: 8th Edition
FearURL Copied!
At the start of each Close Combat round, a unit that is in base contact with one or more enemy models that cause Fear must take a Leadership test, before any blows are struck.
If the test is passed, all is well – the unit has mastered its fear, at least for now. If the test is failed, the unit's fear goes uncontrolled and the warriors cower defensively from the horror before them – all models in the unit have their Weapon Skill reduced to 1 for the remainder of that round of close combat.
Models that cause Fear are themselves immune to Fear, and are not affected by any of this rule's effects (even if their unit fails its test, for example). This includes characters riding Fear-causing mounts, who count as causing Fear themselves (see the Troop Types chapter).