specialized circle

We went down what looked like a servant's narrow spiral staircase, down into the basement. She led me to the back of a storage room and pushed open a heavy, steel door there that opened onto a small, stark chamber, all of concrete, with no other exits. In the center of the chamber was another three-ring summoning circle, but this one's symbols had been made from silver and set into the concrete of the floor. Short bars of what looked like a mixture of silver and obsidian were interspersed around the second circle, creating what would, if the circle was functional, be a very formidable barrier.
But the symbols had been marred, torn, broken. Several from the critical inner ring had been pried up from the floor and were simply missing. Some of the bars had been broken. The circle, as it was, was nonfunctional and worthless - but whole, it would have served to contain Harley MacFinn when he shifted into his beast form. The room was a prison he had created for himself, something to contain the fury of the beast inside of him.
But someone had intentionally marred the circle, made the prison useless.

Fool Moon Chapter 12, Page 131