During Yuji's fight against Shana, he reveals the nature of "Silver" to Margery Daw to stop her from breaking through his barrier. At first it appears as a generic Kick the DogBreak the Haughty moment, but when you think about it, she would've found about "Silver" later anyway, and her contract would've ended then because she would've been devoid of purpose; that way, she can continue without pursuing Silver. Granted, he still did Kick the Dog, and break her he did, but it wasn't really the worst thing he could've done, which reveals the high probability that Snake of the Festival isn't as bad as he appears.
Power of Existence is a metaphor for influence upon reality. All the magic of the series is accomplished by influencing reality. Love is the strongest Unrestrained Spell because when present in a person, love has unlimited influence on their being!
