Phrekyos's stats and abilities depend on the number of main story Key Terms the party has accumulated. Arcane Labyrinth Key Terms do not count towards Phrekyos's power level. There are seven power levels, each one corresponding to a certain number of key terms learned, with the more powerful versions being fought with more words learned. The most powerful version can only be fought if the player has learned all fifteen of the main story's Key Terms.
Level 1 Phrekyos will be fought if the party knows 4 or less key terms.
Level 2 Phrekyos will be fought if the party knows 5-6 key terms.
Level 3 Phrekyos will be fought if the party knows 7-8 key terms.
Level 4 Phrekyos will be fought if the party knows 9-10 key terms.
Level 5 Phrekyos will be fought if the party knows 11-12 key terms.
Level 6 Phreykos will be fought if the party knows 13-14 key terms.
Level 7 Phrekyos will be fought if the party knows 15 key terms.
The player should raise defense with Shell, Protect, and Blink to combat Phrekyos's physical attacks. Since he is resistant to spells, it is better to hit with physical attacks and use Haste and Berserk to increase the damage. Another strategy can be used if one of the characters has the Osmose spell and it is a decent level; one can easily steal all of Phrekyos's MP in one turn with an Osmose that is around level 10. This instantly renders Phrekyos weak as he will only be able to attack.
After defeating Phrekyos, Deumion will recognize the party's potential and will ask what are they searching for. Depending on the party's answer and the key terms that they've used on the three Arcane Labyrinths, they will be awarded either a Elixir or a character's Ultimate weapon.
Also, telling him the Destruction key term wil prompt a battle against Deumion himself with the Destroy Tome as reward, while giving him the Light of Hope key item will award the party the unique Revive Tome.