Firecomb contains a substance similar to honey (only much hotter) and is produced by Fireworm workers as ordered by the Fireworm Queen. It nourishes the fireworms and the hatchlings similar how to honey nourishing bees. It is protected by the Fireworm Queen on Fireworm Island.
The Firecombs were discovered on Fireworm Island inside the Fireworm Nest when the Riders search for a way to save the ailing Hookfang. Snotlout broke off a piece of firecomb, believing it would cure Hookfang, but ended up angering the Fireworm Queen. Though she then used her own fire to save the other dragon.
The Fireworm Queen tracked Hookfang down in hopes he would return the favor she did for him many years earlier. A Cavern Crasher, Firecomb Crasher, attacked the nest, and drove the smaller Fireworms away. In the attempt to fight it off alone, it wounded the Queen. It then attempted to eat the firecombs that contained newly hatched fireworms. But Snotlout and Hookfang helped drive the adhesive dragon off, saving the Queen's young.