[ She hesitates at his question. She can explain-- and she did a bit-- but she feels as if she's already said too much. If she went into more detail, that might give away something about which Noctis has yet to tell his father of the crystal. Saying that the crystal of Eos has burdened him with the memories of the world might lead to Regis asking why there would be a need. That need is somehow tied to Noctis' fate, of which Regis does not know.

This is a problem. Regis, she believes, has all the right to know and more, and as she meets Regis' eyes and sees the kindness within them, her heart aches for what she cannot say. She wants properly explain her part in this to him, but she can't. Or, she'll have to very carefully navigate about it. ​]

It alleviates a stress upon his soul, keeping it safe... and... protects his soul from more stress. The crystal may also physically protect him from a mortal wound, too. [ Even if he was stabbed through the heart, her crystal would repair it. ]

Rest assured, he's still him. There is not a part of my crystal that's imposing upon his psyche or will.