Haddrun, also known as “dragon’s breath” and “blood lightning”, is a narcotic made from the blood of dragons. It iss illegal in most civilized areas. Not because it is inherently dangerous, but because dragons don’t like people hunting them for their blood and have been known to express their feelings on the matter with rampant carnage. People who take it experience a mild euphoric effect and it’s been known to make users feel nigh-invincible when consumed in large quantities.
Far less well known (Arcana or Streetwise DC 17) is the fact that haddrun, made from the blood of blue dragons, is only one of many varieties of drugs made from dragon’s blood.