Cackle Fever

This disease targets humanoids, although gnomes are strangely immune. While in the grips of this disease, victims frequently succumb to fits of mad laughter, giving the disease its common name and its morbid nickname: “the shrieks.” Symptoms manifest 1d4 hours after infection and include fever and disorientation. The infected creature gains one level of exhaustion that can’t be removed until the disease is cured. Any event that causes the infected creature great stress—including entering combat, taking damage, experiencing fear, or having a nightmare—forces the creature to make a DC 13 Constitution saving throw. On a failed save, the creature takes 5 (1d10) psychic damage and becomes incapacitated with mad laughter for 1 minute. The creature can repeat the saving throw at the end of each of its turns, ending the mad laughter and the incapacitated condition on a success. Any humanoid creature that starts its turn within 10 feet of an infected creature in the throes of mad laughter must succeed on a DC 10 Constitution saving throw or also become infected with the disease. Once a creature succeeds on this save, it is immune to the mad laughter of that particular infected creature for 24 hours. At the end of each long rest, an infected creature can make a DC 13 Constitution saving throw. On a successful save, the DC for this save and for the save to avoid an attack of mad laughter drops by 1d6. When the saving throw DC drops to 0, the creature recovers from the disease. A creature that fails three of these saving throws gains a randomly determined form of indefinite madness, as described later.

Magical Contagion

Cheaply made potions and elixirs are sometimes tainted by Cackle Fever, which affects Humanoids only (gnomes are strangely immune). A creature suffers the following effects 1d4 days after infection:

Fever. The creature gains 1 Exhaustion level, which lasts until the contagion ends on the creature. Uncontrollable Laughter. While the creature has the Exhaustion condition, the creature makes a DC 13 Constitution saving throw each time it takes damage other than Psychic damage. On a failed save, the creature takes 5 (1d10) Psychic damage and has the Incapacitated condition as it laughs uncontrollably. At the end of each of its turns, the creature repeats the save, ending the effect on itself on a success. After 1 minute, it succeeds automatically.

Fighting the Contagion. At the end of each Long Rest, an infected creature makes a DC 13 Constitution saving throw. After the creature succeeds on three of these saves, the contagion ends on it, and the creature is immune to Cackle Fever for 1 year. Spreading the Contagion. Any Humanoid (other than a gnome) that starts its turn within a 10-foot Emanation originating from a creature infected with Cackle Fever must succeed on a DC 10 Constitution saving throw or also become infected with the contagion. On a successful save, the Humanoid can’t catch the contagion from that particular infected creature for the next 24 hours.