Mors immedicabilis was a dangerous disease generally referred to as the Incurable Death.
History
Whole planets were wiped out by Mors immedicabilis. The disease was fast spreading, causing pustules and weakness. The victim was usually dead within minutes. As the name suggests, there was no known cure for the disease. Slarn, whose hypochrondia could cause diseases to manifest in himself, died when he suspected he had it. His steward also died of the malady. (BBCR: Slipback)