Groncicle

The Groncicle is a Boulder Class dragon introduced in Dragons: Rise of Berk and also appeared in School of Dragons.

Appearance
Groncicles are covered in snow and ice. Their spines or hunches on their back resemble snowy mountains. They have spikes under their chin which resemble icicles or snow cones.The Groncicle looks like a muscular Gronckle, except that it has a longer body length, covered in snow and ice, as well as lacking a tail bludgeon. It looks like the Groncicle lives in snow or near snow

When Groncicles are frozen for ages, they can turn purple in color. This was shown by the Frozen Groncicle in Rise of Berk.

Description
This arctic Boulder Class cousin of the Gronckle is cold blooded! With ice in his veins and liquid nitrogen fire, water actually freezes around him as he swims.

Liquid Nitrogen Fire
The Groncicle shoots powerful streams of Liquid Nitrogen. Liquid nitrogen can reach temperatures close to -321 °F or -196 °C. This can potentially freeze their victim to death.

Freezing Water
The Groncicle is able to freeze water around it while swimming. This is probably because the ice in its vein causes the water around it to lose heat and freeze. Though the reason for the Groncicle's uncanny behaviour is unknown, one possible purpose is to freeze and trap their aquatic prey in water.

Speed
The Groncicle is known as one of the fastest Boulder Class dragons, as it is much more streamlined than its cousin, the Gronckle. This exceptional speed gives it high maneuverability while in water. Despite most Boulder class dragons are known to be slow flyers.

Titan Wing
Source: Dragons: Rise of Berk.

Groncicles that have reached the titan wing stage change quite a lot. Their body is darker and there are light blue outlines of what seems to be their liquid nitrogen veins. Their wings have white rings and its edges develop small, spikey icicle-like structures. Titan Groncicles' mouths glow purple and their eyes turn pinkish purple. Also, the icy spikes on their tails and under their chins become larger and thicker.

Trivia

 * The Groncicle's name is a combination of the words "Gronckle" and "icicle".
 * Even though the Groncicle is a Boulder Class dragon, it is more sensible to be put in the Tidal Class because, the description states that it swims, and in the Arctic regions, water and ice are everywhere. Meaning that it is a frequent swimmer.
 * It is the only known water-based boulder class dragon.
 * The Grocicle's egg looks like a geometric ice-like shape similar to the Shivertooth's and the Sweet Death's egg.
 * In School of Dragons, the Groncicle has a speed maxed out, meaning the Groncicle is among the fastest, if not the fastest Boulder Class dragon.
 * According to School of Dragons, the Groncicle was first named by Hiccup.
 * The Groncicle's egg has a similar appearence to the orb of frozen futures. Some people, like Trader Johann, can confuse the two of them.
 * The Groncicle's liquid nitrogen fire can also be referred to as ice.
 * The Groncicle seems to have no actual teeth in Rise of Berk. But teeth that resemble a Gronckle's were added in School of Dragons.