The drug commonly referred to as "dark" is heroin, specifically the black sticky form known as "black tar heroin." It is a highly addictive opioid processed from morphine, extracted from poppy plants. This form of heroin is often called "dark," "black tar," or "horse" among other street names
. Additionally, "dark" can be slang related to heroin in the context of county lines drug trafficking, where "dark" or "light" may refer to heroin and crack cocaine respectively
. No other specific drugs are widely known by the slang term "dark" in the provided sources.
