Lesai was an addictive drug banned throughout both the Galactic Empire and the Centrality.
Lesai was a mold that grew on the back of a certain species of lizard, which themselves could survive only in the presence of some rather disgusting plants. These lizards and the plants needed grew mainly on the planets Zebitrope IV and Zebitrope VIII, but could be exported elsewhere. The purplish mold was generally scraped off with a spatula, then rubbed into the hollow at the base of the user's throat. This left a distinctive purple stain that most addicts took to covering up with flesh-colored powder.
Lesai allowed Humans, and perhaps other sentient species, to go without the need for sleep. It thus effectively extended the average life-span by one third.
The governments claimed that lesai had the side effect of turning users into amoral machines with no feelings or compassion for others. However, this does not seem to have been the case, as Lob Doluff, Administrator Senior of the Oseon system was a secret lesai addict himself, and wished so dearly that it did remove feelings so he didn't have to think about things that tugged at his heartstrings.
Bohhuah Mutdah, the richest man in the galaxy, was a lesai addict as well.