The Drakostomes are nematodes (a kind or parasitic roundworm) that were previously contained in the bark of the Panakes. They were used to unleash the deadly Gnomish Plague. In Neverseen, King Dimitar allies with the Neverseen in order to cause the plague, in the hopes that the gnomes would be forced to work as slaves for the ogres.
The Cure[]
The only known cure to the drakostomes comes from the flowers of the Panakes. King Dimitar announced to have the cure to the plague, although it was later revealed to be a fake. When Sophie, Keefe, Fitz, Biana, Dex, Alvar, Calla, Tam, and Linh break into Ravagog they plan to steal the cure but when Sophie and Fitz sneak into Dimitar's mind they figure out in the chest was the plague, not the cure. They didn't want to tell Calla, but she knew from the Panakes roots.
The Sacrifice[]
Calla also knew from the roots that the Panakes were the ancient deceased gnomes. Calla sings a song before telling everyone she must sacrifice herself to be the cure. Sophie originally tries to convince Calla there is another way, but Calla doesn't change her mind. Then the next morning overlooking the ocean was a beautiful tree with braided bark and flowers that turned from blue to pink to purple at Havenfield. The tree's blossoms were the cure for all the gnomes with the plague. Calla’s flowers are used often by Sophie and her friends.
The Discovery[]
The drakostomes were discovered by Dex in a breach to a secret Council vault during Neverseen, using a device called the Twiggler that had to use technology from the trolls, elves, ogres, dwarves, and also gnomes and, suprisingly, the humans . He sees that drakostomes are affiliated with the plague and therefore tries to learn more about them, but the whole mystery is not unraveled until the Council tells the whole story and admit to letting the ogres threaten the gnomes.