Individuals affected by Fear are depicted with sweat droplets dripping out of them. Damage taken by any other source, including Burning, Shocked, and Poison damage-over-time effects are doubled* by the Fear debuff. Damage multipliers from other passives are calculated first before the Fear multiplier 2x is calculated for the total damage. When the health of the affected target drops to 20% or lower, it has a chance of abandoning their team and running away from the fight.
It is not sure if Frostbitten damage is also doubled, as it is a fixed 20% damage.
Lupina, Mangle Jaw, Jabber Clenchjaw, and Tsume have abilities that inflict Fear on their opponents. High king Valkin's to war! (cavalry variant) can also inflict fear to the entier ennemy team for 1 turn.
Heroes
The following heroes have or can inflict/apply Feared:
Terrorstorm (Special Attack): Self and allied Constructs gain 1 Energy, then does a Ranged Lightning attack on all enemies with a chance to Fear. Deals boosted damage to Armored targets.
Unnatural Fear (Trait): Immune to Fear and chance to Fear Beasts on hit. Terror Tooth (Special Attack): Melee Physical Bite attack on target and 1 random enemy with a chance to Fear.
Haunted Past (Special Attack): Ranged Spirit Attack that Haunts the enemy team, with a chance to Fear the initial target (Haunted enemies receive 2x damage from Dark Heroes).
Epic Unbridled Rage (Trait): Self and allied Barbarians are immune to Fear and if they would die, ignores death but grants a shield for a turn (like Ethereal Spirit, HP does not drop below 1). Ignores Shield Piercing & Chaos Damage, happens once per dungeon. (This trait replaces 'Unbridled Rage' when the Epic is unlocked.)
Will of the Wisp (Trait): Immune to Spirit, Lightning, and Light attacks. High resistance (75%) to Paralysis. [Light allies start Dungeons with +1 extra energy]. The text in [brackets] is of rank II of this trait (I/II).
Epic Fiery Soul (Trait): Beasts on this Hero's team have wild and untameable souls, making them Spirit and Fire immune. They take 20% less Chaos damage. (This replaces the 'Fiery Soul' trait once her Epic is unlocked. She keeps her other immunities (such as Fear Immune, etc) from Fiery Soul.)
Dryad Ice (Trait): Starts dungeons in Ice Block, reducing damage taken (90% Damage Reduction) and Debuff immune until their first turn. Can't be stolen, copied, or purged.
Ambush Tactics (Special Attack): Ranged Physical attack on target enemy and all Ranged allies attack the same target, then gain Stealth and become Invulnerable for 1 turn. Starts Powered.
Ice Block (Trait): Starts dungeons in Ice Block, reducing damage taken (90% Damage Reduction) and Debuff immune until his first turn. Can't be stolen, copied, or purged.
The Last Word (Trait): Slow allies and self take 30% reduced damage from Fast enemies. Slow allies revenge attacks twice. Slow allies can't have buffs removed or debuffs added by fast enemies.