Krystallix

General
Krystallix is an alien crystal monster that is an optional superboss you can fight before the final battle. Gaining him by this point allows you to skip a miniboss on your way to fight Treasure King. When he is encountered, he is under the control of the Treasure king, who attached a control devise as he was regenerating from his crash landing, and defeating him will recruit him.

In-Battle
He has multiple points to attack in the form of two to four crystal pillars that can attack as well as a main body. The crystals can be regenerated one per turn and Krystallix can only be defeated by attacking the main body.