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This article contains plot details from the latest books.
Soporidine is secreted from Bucollosiscia, a hybridized bacterium. The bacteria themselves are harmless, but the soporidine is a powerful sedative that can be lethal. When used, the person has no thoughts or dreams. Although it is hard to produce, it can be harvested. Sleep-inducing flowers burned with Everblaze can sustain the bacteria long enough to collect the sedative. The Neverseen made many batches of the soporidine to threaten people with, since they are the only ones with the cure.
Soporodine is soft and gloopy, like paint. It is typically vivid purple when in contact with skin. However, the variety developed by Lady Gisela (used to sedate Silveny and Greyfell) is deep blue due to chemical changes for its effects on alicorn physiology. The antidote for the purple variety is green, and the antidote for the blue variety is orange.