I am Setsuna | Fides' Legendary Spritnite: Dragnarok

Have Fides in your party and head to Gatherington. Enter the cafe and talk to the man in the hood. He will tell you about a stolen spritnite. Then, leave the cafe and another cutscene will occur. After it's done, exit the village on the north side and head to the Fridged Caves.

Remember the area where you fought the last boss? Walk to there. Make sure to use the Save point and head to the center of the area. You will find the monster boy. Later, a dragon appears and you have to fight it.

The dragon is called Dysphormic Monster. It's quite tough. For preparation, make sure you have a character that can do AoE healing (Endir's Aura or Setsuna's Cure II) and equip some spritnites that can boost your defense/attack, and if you have Purikka Cobbler Salad, eat it. It helps you to boost your max HP. Make sure to stock up your Hi-Potion and Athenian Water, just in case.

Be careful whenever its HP reaching low, it will starting to attack you using Dragnarok that can hit all of your party around 150-200 HP.

After the dragon is defeated and the conversation has ended, you will obtain Dragnarok spritnite.