In this fight you won't be trying to kill the Old Sorceress, but rather save her. The fight starts out with four Bodies of Thought. One is Water element, one is Fire element, one is Earth element, and one is Wind element. Every turn the Sorceress gets, she'll use an ability called "Scream" which changes all the Bodies of Thought to a different random element. You can do a whole lot of damage by hitting them with the spell they're weak against, but if you are unlucky, and the Sorceress gets her turn first -- when she gets her turn seems random -- she may cause the Body of Thought that you targeted to change to the same element that you cast. If that's the case, you'll actually heal it. Because the Old Sorceress only has 1,110 HP and the crystals attack for about 100 each with their Grudge and Envy attacks, you probably don't want to waste any time. Instead, just have Seth, Kaim, and Mack use Power Attacks while Ming and Jansen cast Force. (You could also have them use Force as well if you wish) Target one Body of Thought at a time and you'll have them down before the Old Sorceress dies. As an alternative, you can have Jansen equipped with an accessory that allows Spirit Magic, any level, Ming with Spirit Magic equipped, and Mack in your party, have Kaim and Seth Attack or use Power hit, and have the three casters use Shadow, it will only hit the Bodies of Thought, not the Old Sorceress.
The Old Sorceress is fought in the basement of the Old Sorceress’s Mansion. She appears with four Bodies of Thought. The Bodies of Thought are the real enemies and if the Old Sorceress dies, it's Game Over.
The Old Sorceress only has one attack: Scream, which changes each Body of Thought's elemental properties. If you hit a Body of Thought with its opposing element, its next attack on the Old Sorceress will be weaker. If you hit it with the same element, the next attack will be stronger.
On the first turn, the Old Sorceress will Scream before you attack, so any magic spells you use will likely not have as much effect, or actually strengthen the Bodies of Thought. On subsequent turns, Scream will come at the end of the turn, most likely, it may still come in the middle.
Use your first turn to cast Powera or Minda on Kaim, Seth, or Ming, and defend with the others as the Sorceress will scream and throw the elements out of wack immediately. If you have a White-Black Magic Level 2 band, give it to Cooke. If you have crafted any rings with Damage Up and an Element (ex: Damage Up, Earth Damage), this is the place to use them.
Fire elements take more damage from Water attacks
Water elements take more damage from Ground attacks
Ground elements take more damage from Wind attacks
Wind elements take more damage from Fire attacks
Focus Kaim, Seth, and Ming on one Body of Thought by hitting it with the opposite element. Only a magic spell will cause the damage of the Body of Thought to go down (from 70 to about 30 against the Old Sorceress), but your physical attacks will still do quite a bit of damage against it. Use Jansen and Cooke to use spells against the two other elements. This will minimize damage to the Old Sorceress while maximizing your damage against the Bodies of Thought. The battle isn't very difficult and the Bodies of Thought never attack your party directly, however when you attack physically with Kaim/Seth, they will damage them (Mine damage). Heal when necessary and keep switching rings as needed on Kaim and Seth and the battle will finish relatively quickly.