Ageless Ones are the only enemy found in the Sorceress' Mansion that are equally prone to being damaged by your physical attacks as your magic attacks. Because of this, attacks, Power Attacks, Forces... they all do the trick. The problem is, their low defense is offset by their strong offense: they can hit you with both Aquara and Grounda, for a fair bit of damage. You'll usually see them side by side with Soul Armors. In those cases, have your mages take out the Soul Armors with one Flare per target, while Kaim and Seth both focus on one of these guys.