A: I have been asked this a few times, I apologize for the confusion. Here is what the Spell Blade Expertise states:
"You can choose one Novice/Mystic spell per day to inscribe on your melee weapon. After making a successful attack, you may cast the spell automatically. This raises the Energizing State. This spell may be used three times per day."
The confusion arises with the "Novice/Mystic" wording. This means you may inscribe a Novice level spell from any non-unique spell tree/spell (unless you know that realm or can take that unique spell; example: a naturalist could inscribe a Natura spell). Alternatively, you may choose to inscribe a Mystic spell instead.
The Energizing State that is affected is the realm from which the spell originates. Example: casting the Frostbite spell would raise the Arcane Energizing State.