- "I know what people look like on speed. This is... There's more to this. Simpson was so intense, focused, and he's wounded, but not feeling it."
"Probably some kind of combat enhancement for wakefulness. To numb the pain center, push the adrenergic system for strength and stamina."
- ―Trish Walker and Albert Thompson[src]
The Combat Enhancers were created by a military program from an organization known only as IGH. They affect the adrenal gland, causing the subject to constantly produce adrenaline. This grants the subject enhanced strength, immunity to pain and fatigue and accelerated recuperation. However, it also causes the user to become reckless and dangerous, especially to those posing an immediate threat or perceived by the user as such. In the case of a user taking a red pill without a blue pill, they can die.
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Will Simpson previously volunteered for a drug experiment to increase his strength conducted by Doctor Miklos Kozlov; however he left the program as he struggled to keep control of his rage while on the drugs.
Years later, Simpson requested Kozlov's assistance when he was left in critical condition due to an explosion engineered by Kilgrave with a bomb that Simpson himself had planted. Upon agreeing to reenter the program, Kozlov began a treatment and supplied Simpson with a red pill to speed up his recovery.
Once Simpson regained consciousness, Kozlov explained the new protocol in place for the enhancers following an incident in Damascus. According to Kozlov, one red pill would bring him up, two whites pills would keep him even, and one blue pill would bring him down. However, Simpson took an additional red pill as soon as Kozlov left. His heightened adrenaline led eventually to insanity, causing several murders along with the attempted murder of Jessica Jones and accidental assault of Trish Walker.
Trish Walker also took one of the reds in order to fight back against the homicidal Simpson in defense of Jessica, who had already suffered a broken rib. Despite Simpson's warning that without blues to calm her down, she would have adrenaline so high that her brain would forget how to breathe, and that Simpson himself would not need a blue for several hours on account of having built up a tolerance to reds. Trish won the fight, but almost instantly later collapsed and needed to be resuscitated to bring her down from the stimulant.
Will Simpson takes different colored pills, known as combat enhancers, to produce different bodily effects. These pills include red, for increased adrenaline; white, to stabilize the heightened level of adrenaline; and blue, to relax him to keep him alive.
- Enhanced Strength: Due to the effects of increased adrenaline, the user is able to match the strength of an injured Jessica Jones.
- Enhanced Stamina: Due to the effects of increased adrenaline, the user's body produces far less fatigue than normal human beings.
- Regenerative Healing Factor: The user's increased metabolism grants them an accelerated healing abilities, allowing them to heal from cuts, broken bones and bruises overnight. They saved Simpson from the critical injuries he sustained when Elizabeth De Luca exploded near him.
- Pain Suppression: Due to the effects of increased adrenaline, the user can function with catastrophic wounds on their body without showing any signs of pain or fatigue.
In chronological order:
- Jessica Jones