The Crystal attacks with magic and can make use of the Ring Lock technique. It can also use the Yuke Magic Thread, throwing a Fire Magicite on the floor to use with the Magic Thread to create a trail of fire that follows the player from the Magicite and can cause very serious damage, so it is advised to either moving out of the way quickly or taking the Magicite.
Stock up on Blizzard and Thunder before the battle. Once the battle starts, keep spamming with physical attacks and cast Blizzard or Thunder every once in a while. Avoid the Fire attack and grab the Magicite. Repeat, while healing occasionally and the battle should be a snap.