This champion has -3 DMG and may not attack the unit that frightened it.
Frightened is a good way to reduce the damage potential of enemy champions. The ability Psychological Warfare works with the Frightened condition
Sources of FrightenedAugment
Counters to frightenedAugment
There are several abilities that can prevent a champion from becoming frightened: the ability fearless mostly, that comes in several other abilities like Boon of the undead and prestige.