|Cost to buy||$2000 per syringe|
|Cost to sell||None. Nobody sells it except Dr. Harper.|
PAX 21 is a highly addictive super-steroid. The drug, usually injected in a constant supply into the base of the neck would instantly transform someone into a hulking mass of unbridled physical strength. Peter's apparatus included a special "boost" button to give him a jolt of PAX 21 when needed.
However, as the drug wore off or when the user was cut off from its constant supply, their body would rapidly grow to an even larger hulking mass and lose all intelligence levels at which point the user would suffer from massive, debilitating withdrawal, usually accompanied by terrifying hallucinations.
Nightmare became addicted to the drug while searching for a way to cope for his physical limitations and imperfections, forcing him to eventually lock himself in his apartment to "detox" himself when he realized how dependent on it he had become. Later, it resurfaced as the power source for Doctor Harper , who used it to overpower and cripple Sai .