Fallout Wiki
Fallout Wiki

A unique case amongst the serum trials, initial subjects expired within seconds, exhibiting major trauma to the body on scale previously unknown.

It was only after reviewing slowed-down footage of the initial tests that the team realized test subjects were essentially shredding their own bodies when attempting to move, the incident happening so fast as to be nearly indiscernible to the naked eye.

Highly diluted solutions were used for subsequent tests, with doses increased slightly until physical limitations were reached.
The Whitespring bunker terminal entries

Speed Demon is a mutation in Fallout 76.


Positive effects
+20% movement speed and reload speed.
Negative effects
Increased Hunger and Thirst accumulation.


Having this mutation provides the highest possible movement speed bonus, making all other movement speed modifiers redundant. This includes the Squad Maneuvers perk, Sleek armor leg mods, the Fixer and legendary weapon modifiers that provide bonus movement speed when aiming.


  • Icon pc.png Icon ps4.png Icon xboxone.png The mutation reduces the efficiency of stimpacks and other sources of healing.[verification overdue]
  • Icon pc.png Icon ps4.png Icon xboxone.png The Class Freak perk has no effect on the downside of this mutation.[verification needed]
  • Icon pc.png Icon ps4.png Icon xboxone.png The negative effects of this mutation are not suppressed while under the effects of Rad-X.[verification needed]