Frozen

Episode 14 of Defenders of Berk

Synopsis
Hiccup and Toothless return from a mission to find Berk mysteriously empty. They discover that the village has been overrun by Speed Stingers, a venomous non-flying dragon that has trekked across the frozen sea to Berk and driven everyone out of town. Hiccup must find a way to drive the Speed Stinger horde away from Berk.

Source
How to train your Dragon Website

Trivia

 * First appearance of the Speed Stinger