Hardshell

The Hardshell is a monster based on a mollusk. "Hardshell" is derived from the hard shell that protects it.

Biology
Most of the Hardshell is protected in a thick, hard, violet shell, with a number of cracks on it from predator attacks. This means that the counting the number of cracks is a great way to estimate the age of the Hardshell. The only parts that are left exposed are its face and legs, which shows its black-fleshed interior. The purple shell edges around its face and legs are significantly thicker, and the edge at the former has a multitude of sharp, pink spikes. It also has a hard, curvy tail.

Hardshells are not very active monsters, and often only need to eat once a week. They feed on algae growing at wet beach rocks. The only other time Hardshells become active other than feeding is during mating and reproduction. The Hardshell, after finding a mate, would dig a hole to lay two to three eggs in. The partner Hardshells than remains relatively motionless on top of their "nest" until the eggs hatch, willingly fasting to protect their future children. Baby Hardshells would than dig out of their "nest" and live their life, while the parent Hardshells would lay another batch of eggs.

Behavior and abilities
Thanks to their extremely tough and durable shell making them oblivious to threats, Hardshells are passive for most of their lives. However, when they are attacked by a predator that they find to maybe able to crack their shell open, they do the following.

Sharp spikes. The Hardshell makes sharp spikes suddenly jut out of its shell to repel the attacker.

The only time they become aggressive is when their eggs are in danger from a predator, in which case they do the following.

Enrage. The Hardshell enters a state of pure rage, gaining extreme agility and power, as well as gaining an empowered version of Sharp spikes with longer and sharper spikes. The Hardshell than rushes at the enemy repeatedly with its spiky body until the enemy falls or flees.