Dark Deep

Dark Deep is an island that appears in "Quake, Rattle and Roll". It also appeared on the app How to Train Your Dragon: Flight of the Night Fury.

Description
The craggy and rocky legendary home of the Gronckles. It’s cavernous with lots of rocks for Gronckles to munch on.

It is also home to the Catastrophic Quakes–a fearsome Boulder Class dragon that is muscling out the Gronckles for their food source. But the Quaken might have a hidden secret, and the dragon riders must figure it out before the Gronckles are displaced forever.

Location and Physical Geography
Dark Deep is both the ancestral home of the Gronckles in the Barbaric Archipelago and is the only known habitat of the Catastrophic Quaken. According to Dragons: Rise of Berk, Tide Gliders also live in the area. The team first discovered it on the Dragon Eye. Dark Deep is quite deserted, with plenty of rocks and an extensive network of underground tunnels where Gronckles dwell to hide from the Catastrophic Quaken.

Trivia

 * Dark Deep's terrain is similar to Outcast Island.