Liberty, or "Lib", is a powerful designer drug manufactured by the NWO using, essentially, distillate of Shadows.
What exactly goes into Lib may change from batch to batch; the recipe and the process of its distillation are more art than science, and none can be made without the "base material" possessed by the NWO. The base material in question is actually Shadow essence, which is mixed with heavy stimulants and psychotropic substances to create the drug itself. In its final form, the drug takes the form of white pills which may be ingested orally or crushed and melted for smoking or intravenous injection.
The drug causes heightened physical properties, the temporary manifestation of powers resembling that of Persona, and madness. The effects eventually wear off but can be quite long lasting and resemble those of long-term methamphetamine abuse; they include eventual heart and liver damage, neuropathy and, finally, lasting brain damage.
All current theory says that the drug could be enhancing the power of the "Shadow" part of each person which resides in their id. This is tied in to the fact that Personas are simply tamed Shadows, and a person using a Persona who consumes this Shadow-laced drug is giving their Shadow power. This makes the Persona appear more powerful (since an unchained Persona, a Shadow, is often more directly powerful and destructive due to lacking limiters intended to protect its wielder), but carries increased risk of Shadow-Possession. Even normal people without Personae can find themselves more susceptible to Shadow-possession if they take the drug, but arguably those who have already manifested the power of the mind are at greater risk. To take Lib is, in essence, to make a temporary deal with one's Shadow for increased power. However, in releasing the hatred and aggression which the umbral mix can bring forth, the subject opens themselves to the host of associated darknesses.
Despite its eventually fatal effects, Lib is extremely popular -- especially when it's on the street and could be cut with anything. Mostly it is used by criminal agencies or those who have some grudge to settle, as it is essentially a death sentence in any large dose. However, the momentary exhilaration, increase in power, and amazing manifestation of supernatural abilities is enough to turn a lightweight into a raging berserker capable of killing and quite possibly eating an entire police force. This stuff sells high and is often used by private armies or exported as an illicit trade commodity; its manufacture is tightly controlled by the NWO, one of few groups able to contain and process Shadows and thus produce the "wonder" drug.
"Street" Lib, like SEBEC Lib below, has ceased to be available in any form. In October 2010 dealers abruptly found themselves faced with a dwindling supply, finally running out for good in approximately August 2011. The exact date the manufacturing ended is unclear, but seems to coincide with the rift that occurred between Takahisa Kandori and Tatsuya Sudou in September 2010; it was during this time that Sudou withdrew Masquerade support for the manufacturing facilities and personally destroyed several of them, the latter presumably out of sheer spite.
With the demise of Takahisa Kandori, "SEBEC-Lib" as far as anyone knows no longer exists. The rest of the NWO has other methods of ensuring strength and loyalty in their ground troops. SEBEC Lib, when it was 'common', was dosed out to SEBEC security forces and was deemed a more 'stable' version of the drug. SEBEC Lib was also doled out to some experimental subjects to boost the strength of their Shadow.