blocks a bunch of vampires

Seven or eight vampires were within fifty feet of me, and coming fast. Thomas sprinted toward me, a knife gleaming in his hand, and hit one of the vamps from behind. He cut open the vampire's belly with a single slice, and the creature collapsed to the ground. "Harry, get out!"
"No!" I shouted. "Get Susan out of here!"
Thomas gritted his teeth, but changed course. He leapt up onto the first-base dugout and hopped neatly over the rail into the stands.
No help there, and there wasn't time to look for options. I crouched and concentrated, chanting, "Defendre, defendre," in a steady litany. It was difficult to do without my shield bracelet to focus it, but I brought up all the defensive energy I could manage in a dome around me.
The vampires hit it, slamming against it in mindless, shrieking rage. Any one of them could have flipped my car over lengthwise with only a little effort. Their blows against the shield could have crushed concrete within seconds, and I knew I was not going to be able to hold the defense in place for long. Once it went down, they were going to literally tear me limb from limb. I gave the shield my all, and felt them slowly breaking it down.
Then there was a roar, and a flash of brilliant light. A jet of fire streaked over me and took one of the vampires full-on in the head. It burst into flame, screaming and waving its too-thin arms, and went down onto the field, thrashing like a half-crushed bug. My shield collapsed, overloaded, and the bracelet began burning my wrist. I crouched lower.

Death Masks Chapter 30, Page 267-268