Sky Fungus (5e Disease)
From D&D Wiki
This fungus tends to rain down on people living in windy, mountainous areas.
Stage 0: Once contracted, the host must make DC 13 Constitution saving throw every day. After 3 successes, the disease fades. After 3 failures, signs of the disease begin to show, and no more saves may be made.
Stage 1: For the first 1d3 + 2 days, the afflicted has severe headaches that get worse the further downwards the afflicted travels, and are alleviated by climbing upwards.
Stage 2: For the next 3 days, spores begin to appear on the back of the afflicted's neck.
Stage 3: Upon Stage 3, the afflicted must make a DC 13 Constitution saving throw, or be forcibly compelled to climb as high as possible, upon which Stage 4 will begin. Every day, or every time the afflicted is harmed, they may make another save.
Stage 4: The spores on the back of the afflicted's neck rupture, causing them to take 21 (6d6) poison damage, and suffer two levels of exhaustion, and spread the fungus over a large area. The afflicted returns to Stage 0 of the disease and may either show symptoms of it again, or be free of the illness.