Fear

"Weapons with Fear capabilities can scare enemies away resulting on them fleeing for a period of time. Some enemy types are more courageous than others, so scaring them is not always assured."

- In Game Description

In Deep Rock Galactic, certain weapons, weapon mods, grenades, and perks are able to inflict the Fear Status Effect on Glyphid enemies (excluding Brood Nexus), Huuli Hoarders, and Mactera enemies.

Sources of Fear
Driller
 * CRSPR Flamethrower T4.A "It Burns!" applies a 20% Base Fear Chance to enemies from every particle fired by the weapon (default flow rate is 6 particles/sec).
 * Reinforced Power Drills apply 50% Base Fear Chance to enemies every time it damages them.
 * Satchel Charge T4.A "Big Bang" applies 100% Base Fear Chance to enemies within its damage radius plus 10m.
 * HE Grenade applies 100% Base Fear Chance to enemies within its damage radius.

Engineer
 * "Warthog" Auto 210 T5.A "Turret Whip" projectile applies 100% Base Fear Chance to enemies within its 1.5m damage radius.
 * "Stubby" Voltaic SMG Overclock "Turret EM Discharge" applies 50% Base Fear Chance to enemies within a 5m radius of the turret that the explosion is centered on.
 * Deepcore 40mm PGL applies 100% Base Fear Chance to enemies within its damage radius.
 * Plama Burster applies 100% Base Fear Chance to enemies within the burst damage radius upon each burst detonation.
 * Proximity Mine applies 100% Base Fear Chance to enemies within its damage radius.

Gunner
 * "Lead Storm" Powered Minigun T5.A "Aggressive Venting" applies 1000% Base Fear Chance to enemies within a 10m radius around the Gunner upon overheating.
 * "Thunderhead" Heavy Autocannon T5.B "Suppressive Fire" applies 50% Base Fear Chance to enemies within 1m of bullet impact, either on terrain or enemies.
 * Sticky Grenade applies 250% Base Fear Chance to the enemy directly impacted, and 100% Base Fear Chance to all enemies within its damage radius upon detonation.

Scout
 * M1000 Classic T5.B "Precision Terror" applies 250% Base Fear Chance to enemies within 4m of any enemy killed with a Focused Shot to a Weakpoint.
 * Jury-Rigged Boomstick T5.B "Fear the Boomstick" applies 50% Base Fear Chance to enemies within a 5m radius around the Scout every time the trigger is pulled.

Other
 * Active Perk "Field Medic" Tier 4 applies 1000% Base Fear Chance to enemies near the dwarf's downed body, accompanied by a bright flash of light.
 * Active Perk "See You in Hell" applies 1000% Base Fear Chance to enemies near the dwarf's downed body, accompanied by a bright flash of light.
 * Bosco revive applies 1000% Base Fear Chance to enemies near the dwarf's downed body, accompanied by a bright flash of light.
 * Bosco T4.A "Fear the Rocket" applies 50% Base Fear Chance to enemies within the rocket's damage radius.

Effects on Enemies
If the Fear Status Effect gets applied to ground-based enemies like Glyphids or Huuli Hoarders, they should stop what they're doing and attempt to flee from the source of the Fear. Sometimes this is able to interrupt a Praetorian spit attack or Radioactive Praetorian roar attack, but it's not consistent. If an enemy is running away from a source of Fear, they gain a "Flee" movespeed multiplier of x1.5 (with some exceptions, see below) until they have moved 10m away from the source of Fear. Once the Fear Effect has ended, they resume normal behavior.

Similarly, applying the Fear Status Effect to Mactera enemies will cause them to cancel their current attack or move command and fly 10m away from the source of Fear at normal speed before resuming normal behavior. From observation, it appears that Fear isn't able to cancel Mactera Bombers' strafe attacks.

Probability to Inflict Fear
For most enemies in the game, the probability to inflict Fear on them is the listed "Fear Factor" percentage. Certain enemies have Fear Resistance, though, which makes it harder to inflict Fear on them. Below is a table of all enemies in DRG that have Fear Resistance, what their Fear Resistance is, and the effective probability that they will have Fear inflicted on them based on various Base Fear Chances. Any values over 100% can be seen as equal to 100% since that would be a guaranteed application of the Fear Status Effect.

The probability that any given source of Fear Factor will inflict the Fear Status Effect on any given creature is as follows:

Probability to inflict Fear = Base Fear Chance x (100% - Enemy's Fear Resistance)

Such that if an enemy's Fear Resistance is 100%, they cannot have Fear inflicted (with some exceptions, see below).

Interaction with other Crowd Control Status Effects
Once the Fear Effect has been inflicted on an enemy, their only active command is to move 10m away from the source of Fear before they can resume normal behavior. As a result of this, Slowing an enemy either before or during the Fear effect will extend the Fear duration because it takes them longer to reach the goal distance. Similarly, Stunning or Freezing an enemy during the Fear Effect will "pause" the effect because they are unable to move. As a result of this behavior, Stunning, Freezing, or Slowing enemies that have had the Fear Effect applied to them is a very effective form of Crowd Control stacking because it functionally extends the duration of the Fear.

Duration of Fear Status Effect
This isn't fully confirmed yet, but from observation it appears that the duration of the Fear Effect is tied to the distance traveled, rather than a set time duration like the Stun Status Effect. From testing, it appears that the goal distance to travel is around 10m. As a result, enemies that have faster Max Movespeeds will reach the goal distance sooner, therefore having a shorter duration of Fear Effect than their slower counterparts. Using this logic, Glyphid Exploders and Swarmers should be Feared for the least amount of time, while Glyphid Praetorians should be Feared for the most amount of time. As mentioned above, slowing enemies either before or during the Fear Effect will increase the time it takes to travel the full distance, and by extension increase the time that the enemies are Feared.

At its core, the duration of the Fear Effect is just how long it takes a particular enemy to traverse the goal distance, which can be expressed as Time = Distance / Speed. Initially, the Speed in the denominator is just the enemy's Max Movespeed, but then we have to account for several movespeed modifiers. As mentioned above, when ground-based enemies have the Fear Effect applied to them, they gain a x1.5 "Flee" movespeed multiplier. In addition, each Hazard Level has a movespeed modifier that applies to all enemies, ranging from 0.8 - 1.1. Finally, if the enemy is slowed by anything (like Neurotoxin's 30% slow, IFG's 75% slow, or Electrocute's 80% slow) the movespeed needs to be multiplied by (1 - Slow) so that the movespeed is reduced appropriately.

Summing it all up:
 * Let T be the duration of the Fear effect, or how long it takes this particular enemy to travel the full 10m distance
 * Let M be the creature's Max Movespeed (terms of m/sec)
 * Let D be the Difficulty Scaling modifier (ranges from 0.8 - 1.1 depending on Hazard Level)
 * Let S be the movement Slow applied to the enemy, ranging from 0 (no slow) to 0.8 (Electrocute DoT Status Effect)

\[ \begin{align} Time &= \frac{Distance}{Speed} \\ \\ T &= \frac{10}{1.5 * M} * \frac{1}{D} * \frac{1}{1.0 - S} \\ \\ T &= \frac{10}{1.5 * M * D * (1.0 - S)} \end{align} \]

Disclaimer: Mactera enemies don't seem to gain the same x1.5 Flee multiplier, nor do they use their Max Movespeed to achieve the goal distance. As such, the above formula should only be used for ground-based enemies, and not for Mactera enemies.

Special Cases
Although under normal conditions Glyphid Oppressors, Bulk Detonators, Crassus Detonators, and Dreadnoughts cannot have the Fear Status Effect inflicted upon them since their Fear Resistance is 100%, there are four exceptions:
 * Field Medic revive
 * See You in Hell explosion
 * Bosco revive
 * Shield generator

All three of those sources of Fear are accompanied by a bright flash of light and ignore the normal Fear Resistance check, causing them to have a 100% chance to inflict Fear on all enemies. When this happens, the "Flee" movespeed multiplier is changed to x2 for Glyphid Oppressors and x1 for Glyphid Bulk Detonators, Crassus Detonators, and Dreadnoughts.

Miedo