Shellcased are quite small compared to normal demon beasts, approximately four or five feet long (guesstimate.) They have six legs, three on each side of their body, and two bulbous red eyes on the front of their shell. The shell itself is shaped strangely-it has a massive peak on the back, shaped like a mountain, with red markings on the end.
Shellcased group together into hordes, gigantic armies of beasts. They attack by swarming an enemy ruthlessly, foregoing all tactics and charging at their foes. Although they are easy to kill, there are far too many of them, and they devour their target with ease.
A large horde of shellcased attacked Alfheim, where Fremmevilla's Ether Reactors are made. They would have overwhelmed the defenses present, but the Order of the Silver Phoenix attacked the horde from the side, splitting it and enabling the Silhouette Knights to crush the bugs. The horde then was destroyed quickly.