Use half vampires and mortals

"Means they'll have guards there," I said.
"True. We'll have to silence them. It can be done. If we can move fully through the galleries, we'll be within two hundred feet of the base of the temple. That's where we think they'll be performing the ritual. In the temple."
"Plenty of temples got built on top of ley line confluences," I said, nodding. I studied the map. "A lot can happen in two hundred feet," I said. "Even moving fast."
Martin nodded. "Yes, it can. And, if our various intelligence sources are correct, there are more than a thousand individuals nearby."
"A thousand vampires?" I asked.
Martin shrugged. "Many. Many will be their personal guards. Others, the . . . highest-ranking servants, I suppose you would call them. They are like Susan and myself. There may also be mortal foot soldiers, there to keep the sacrifices in line."
"Sacrifices, plural?"
Martin nodded. "The ceremonies of the Red Court of old could last for days, with blood sacrifices made every few minutes. There might be a hundred or two hundred others chosen to die before the ritual."


Changes Chapter 39, Page 415-416