This serum could enhance a person's speed, strength and agility and could heal wounds. However, it had the side effect of making it's user feral and more aggressive.
The serum was created by Dr. James Reeves. He used it on hiself and became more feral. Several months after this Mariah Crawford tracked Reeves down and he gave her a vile of the serum. Reeves then told Mariah that the serum was capable of curing any injury. While saving Mariah from some hyenas, Sergei Kravinoff was severely injured. Against Reeves warnings Mariah used the serum on Kravinoff and it was able to heal his wounds. However, the serum made Kravinoff more feral and more aggressive just as it did to James Reeves. Kravinoff then took the name Kraven the Hunter. Mariah was eventually able to find a cure for the serum and turn Kravinoff back to normal.