Obscura is a widely-used recreational drug among the people of the Imperium of Man. Though this drug is prohibited under Imperial Law and the subject of widespread crackdowns in the ranks of the Astra Militarum, obscura remains a widely used narcotic among Imperial subjects. Smugglers can make a good living importing and selling the drug to all classes of Imperial civilians and military personnel.
Obscura-users enter a dreamlike state for up to five solar hours which is considered quite pleasant if somnobulent, however up to 10 solar hours hours after the effects wear off, they enter a deep depression, unless another dose of obscura is taken. Obscura can prove highly addictive, and the loss in efficiency found among populations where obscura addiction is rampant is why the substance has been banned across the galaxy.
- Only War: Core Rulebook (RPG), pg. 199