Zydrate

Zydrate is an expensive, highly addictive pain killer that has a cheaper, illegal counterpart on the black market, usually sold by Graverobbers. It is a blue, glowing liquid that seems to be some kind of essence extracted from the dead. Zydrate is administered into the body via a Zydrate gun.

Trivia

 * According to early interviews, Zydrate was discovered when doctors searched for a chemical reason for near-death experiences, then made a synthetic version of the compound they discovered for use in surgery.