Banshee is the drug that Colossus revealed he was using to help him with his powers. Without the drug, Colossus was unable to even move his massive metallic body. It was Discovered by Charles Xavier and Magneto in the Savage Land while experimenting on Logan a.k.a. Wolverine.
The drug is effective as it is addictive, triggering secondary and tertiary mutations within those under it's intake. It also causes severe psychological effects on the user causing them to become power mad and mentally unstable. Eventually developing an insurmountable need for more just to keep themselves from falling apart due to substance withdrawal.
Either bestowing supernatural powers onto those whom aren't physiologically augmented in any way. While greatly magnifying the abilities of mutants who take it to inconceivable levels.
Largely comprised of Fentanyl, Mutant Growth Hormone, Testosterone, and Dopamine. It could be found and harvested from the blood of Earth-1610's counterpart of Wolverine. Who described it as a "liquid nightmare" due to it's addictive and lethal attributes causing full on fluctuation in personal composure both in mind and body.
With users becoming more and more unbalanced with each use, some of whom suffering a power overload which can be lethal.