"Fire."
"No way! Fire Magic is flashy, but not the most powerful. What's the Prime Law of Magic?"
"We can only manipulate - never create."
"Exactly. No flame; no Fire Magic."
"Earth then."
"Keep you away from stone and you're powerless."
"Alright, Air. Air is everywhere."
"True, but Air Magic is slow. Think: What's the most powerful Magic of all?"
"I thought that's what we were debating."
"Of all Magic. Even illegal."
"Blood, but they say it's not really more powerful, just easier."
"Blood Magic does take dangerous shortcuts, but it's also powerful."
"Your point?"
"What's Blood made of?"
"...Water?"
"Water."