Karak-lung was a respiratory disease found in the Dark Dwarf city of Thuldûmkarak. It arose from breathing the thick smog that filled the cavern, created by the city’s forges, smelters, and foundries. The cavern was poorly ventilated, which allowed smoke, soot, and noxious fumes to build up over time. Any air-breathing creature who spent at least a full day in Thuldûmkarak risked developing the illness, though the dwarven and Derro residents of the city were less affected due to long exposure.
The chief symptom of karak-lung was a harsh, persistent cough that worsened as black phlegm built up in the sufferer’s lungs. The disease caused weakness, shortness of breath, and made strenuous activity difficult. The coughing fits also disrupted speech, which could prevent spellcasters from completing verbal components. If untreated, karak-lung could become fatal within a week as the airways grew completely clogged. Magical cures such as cure disease could clear the condition instantly, but those who remained in the city risked contracting it again.