Ymir

The Ymir, also known as Whelk or monster who eats thunder. It is faced at the end of the Narshe Mines during the raid on Narshe. When the imperial forces are in front of the frozen esper's room, one of the Narshe guards sends Ymir to attack the opposing forces, as a last stand against the invasion. It is one of the strongest creatures tamed by the Narshe guards. Only one of the two parts needs to be defeated. The head is the easier part to kill, but every ten seconds it hides in the shell and becomes immune to damage until it reappears. The head attacks with a physical attack and Slime, which inflicts slow on a character. Attacking the shell prompts it to counter with Megavolt, which will take a large chunk of HP from you and the party. While it is possible to destroy the shell, it will take a long time to destroy it due to its massive HP. Ymir can use Megavolt six times before it runs out of MP.