From Lost Fables Wiki
Occasionally, when an Il’ha Dreams, they will come into contact with a Dreamworm, usually by falling face-first into mud or a river in the Primordial Dream.
Direct to host, then back into the Dream
Il’ha of any court, and the more an Il’ha Dreams, or visits the Primordial Dream physically, the more likely they are to eventually encounter one of these things.
Asymptomatic for several days, after which a persistent headache will form, slowly getting worse and worse. Around the end of the first week, sleeping becomes significantly more difficult, growing into full-blown insomnia by the end of the first month. Sometime after the first two weeks, vision begins to become blurry, sounds and smells become less distinct, and the headache continues to get worse, eventually plateauing at a place the host can generally continue about their business. Sometime after the second month, and usually before the third, the person will suddenly fall into a deep coma and be physically yanked into the Primordial Dream, where their skull will split open and a foot wide butterfly with geometric black-and-white markings will sprout from the wreckage of their head. It will go and lay several hundred more eggs in the soft mud of a nearby riverbed, usually before becoming prey to something else.
Left untreated, this will always kill.
There is a specific beet red root- Cas’ Root, named after the Il’ha who found it- which grows in the Primordial Dream. Though it tastes foul and bitter, grinding the root up into a pulp and drinking it daily will cause the symptoms to recede and eventually cease. It is presumed that the dreamworm is killed by this and somehow expelled, because they cannot be found in the body after the host’s death.