Something like:
Instead of:You close your eyes for a moment and reach out with your mind to read the pattern of the spellgem in your hand. You trace the lines of the power woven through the gem over and over until you are able to completely comprehend the pattern for yourself. Just as you reach this moment of enlightenment and learn to cast Lifesnuff unaided, the spellgem crumbles to dust in your hand. You acquired mastery over life and death, your enemies shall succumb to your magics.
The message should be based on the capstone's effect.You close your eyes for a moment and reach out with your mind to read the pattern of the spellgem in your hand. You trace the lines of the power woven through the gem over and over until you are able to completely comprehend the pattern for yourself. Just as you reach this moment of enlightenment and learn to cast Lifesnuff unaided, the spellgem crumbles to dust in your hand.