Wall of Thorns Knowledge

"All right," she said. "Let's get out of here."

"No," I said. "I'm not done." I recovered my valise and my staff. "I need to get through those thorns."

"You can't," Elaine said. "Harry, I know this spell. Those thorns aren't just pointy, they're poisonous. If one of them scratches you, you'll be paralyzed in a couple of minutes. Two or three will kill you."

I scowled at the barrier and settled my grip on my staff.

"And they won't burn, either," Elaine added.

"Oh." I ground my teeth. "I'll just force them aside, then."

"That'll be like holding open a screen door, Harry. They'll just fall back into place when your concentration wavers."

"Then it won't waver."

"You can't do it, Harry," Elaine said. "If you start pushing through, Aurora will sense it and she'll tear you apart. If you're holding the thorns off you, you won't be able to defend yourself."

Summer Knight Chapter 33, Pages 428-429