Gronckle

Description
The Gronckle is a medium sized Boulder class dragon that appears in the How to Train Your Dragon franchise. Gronckles are tough, resiliant, and chow down on rocks to produce a lava. Gronckles are also known to produce Gronckle iron, an iron made by consuming several types of rocks. This iron is very light but it is also very durable. It was discovered by Fishlegs Ingerman and Meatlug.

Behavior
Gronckles are described as lazy dragons, often sleeping in communal heaps. They have been known to fall asleep while flying, waking only when they crash into the ocean or the side of a mountain. They are slow in the air, but they are very manueverable, able to fly backwards, sideways, and even hover.

Gronckles can be cranky at times, but they are very social and sweet dragons. If you manage to train a Gronckle(which is very easy) it will be loyal to you and love you forever. They enjoy spending times with their owners, and are very playful. However, Gronckles can be territorial and attack if needed.