Carotid may or may not be a hallucinogen. It grows from a plant similar to spireblack in deep, dark parts of the city of Spire. Taking it changes your perceptions in such a manner than you can see which parts of the city are “alive” – which things breathe or pulse, which rocks are skin or metals bone. Or perhaps the city has always been alive, and Carotid allows you to see the soul of the city as it truly is. Who can say?
This is, to say the least, an acquired taste, and Carotid is not one of the more popular drugs in the city, although there was a brief vogue for it some decades ago, when a school of artists painted what the saw while taking it, increasing interest in the drug.