This egg was only available in Egg Cave's Cash Shop Park for December 2014.
Roknatun eggs are coated in a hard black substance similar to obsidian. As the Roknatun inside grows and nears hatching the substance cracks and beings to fall away revealing a second icy blue shell underneath.
Unlike Rencups Roknatun are not friendly and are actively hostile to anyone that enters their territory. Roknatuns can breath razor sharp ice needles at their foes, making them extremely dangerous. It is advisable to stay far away from a Roknatun's territory. This makes glacier climbing on Ark almost unheard of as many of Ark's glaciers are inhabited by Roknatuns.