When Trader Johann delivers mass quantities of metal to Berk that came from Breakneck Bog, the island becomes infested with Smothering Smokebreaths, that steal the town's metal to build a new nest. With no metal, and especially no weapons to protect their village, Hiccup and the others must find a way to get rid of the rogue dragons, only to discover that the Smokebreaths' appearance was planned as an attack by Dagur the Deranged.
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Complete story — includes the ending
When Trader Johann delivers mass quantities of metal to Berk that came from Breakneck Bog, the island becomes infested with Smothering Smokebreaths that steal the town's metal to build a new nest. With no metal, and therefore no weapons to protect their village, Hiccup and the others must find a way to get rid of the rogue dragons, only to discover that the Smokebreaths' appearance was planned as an attack by Dagur the Deranged.
Sources and content license
Source and revision history · Adapted from Wikipedia contributors, List of DreamWorks Dragons episodes. HTML formatting and reference markers removed. · Content license