Prevents Regen

As if sensing where I was looking, he talks of his arm.
“This? Shiki Ryōgi again, if you haven’t already guessed. I expected it to start healing in short order, but so far that hasn’t happened. I suppose it’s the nature of her spell of death. A wound will heal, but this arm is now truly ‘dead.’ Alaya did say to me that life in its true and pure form was the domain of sorcery beyond him.”

Kara no Kyoukai 7: Murder Speculation (Part 2) Chapter 2 - page 169