Bab 150: After ritual - Part 8

I quickly took Violet and jumped out of the sigil, seeing it on fire. The fire came without warning, rushing in to burn the ground along with the lines on the sigil as if they were the fuel for its flame. The blazing golden sparks outshined even those who shone in the sky, leaving us on the ground bewildered.

"Did you do this?"

"No…" she shook her head, watching the fire with pure astonishment. "I—I didn't, right?"

The fire quickly showed us the glory of its flames, devouring almost everything in its path. It was getting bigger, but never to the point where it went beyond the sigil. It was burning the circle around the sigil, trapping the children inside between the flames and separating us from them.

Is this what happens when you mix the blood of a white witch and a black witch? They caught on fire? Or, is this someone else's doing? There could be two possible answers.