Krystal, who you might remember as one of the ladies during Sidequest 089, wants to conduct an experiment with a spell called Rejuvenate. She wants to test to see if this spell can be used to reverse the aging process. Rejuvenate is a spell that unlocks upon leveling the Spellworks in Evermore to three. You also need to place Leander in the facility, since you need the Tactical Wizardry skill in order to research it. Once you have the spell, return to Krystal to finish.