Firecomb

Firecomb is a substance similar to honey (only much hotter) and is produced by Fireworm workers as ordered by the Fireworm Queen.

In Defenders Of Berk
Firecomb was discovered on Fireworm Island inside the Fireworm Nest. Snotlout broke off a piece of firecomb, believing it would cure Hookfang, but ended up angering the Fireworm Queen.