Erlking is close to Mab's level

"A book called Die Lied der Erlking."
"Oh, I've read that one." She scrunched up her nose, eyes distant for a second, then said, "Two copies, right-hand shelf, third row from the top, eighth and ninth books from the left."
I blinked at her, then went to the shelf and found the book where she'd said. "Wow. Good call."
"Eidetic memory," she said with a pleased smile. "It's... sort of my talent." She gestured vaguely with the hand she'd touched me with.
"Must come in handy during inventory." I checked the shelf. "There's only one copy, though."
She frowned, then shrugged. "Mister Bock must have sold one this week."
"I bet he did," I said, troubled. It bothered me to think about Grevane standing in a store, speaking to people like Bock or Shiela. I pulled the cage closed and started slowly for the front of the store.
I opened the book. I'd heard it referenced before, in other works. It was supposed to deal with the lore around the Erlkoenig, or Elfking. He was supposed to be a faerie figure of considerable power, maybe a counterpart to the Queens of the Faerie Courts. The book had been compiled by Wizard Peabody early last century from the collected notes of a dozen different crusty wizards, most of them dead at the time, and was considered to be a work of nearly pure speculation.

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I raked my fingers through my hair. "And nothing. It's a collection of essays about a particular figure of faerie lore called the Erlking."
"Who is he?"
"He's one of the high sidhe," I said. "And he isn't part of Winter or Summer. He's a wyldfae."
"Powerful?"
"Very," I said. "But just how powerful he is varies depending on who was writing about him. Some of them ranked him among the top faerie nobles. A couple claimed he was on par with one of the Faerie Queens."
"What does he do?"
"He's some kind of hunter spirit," I said. "Associated with all kinds of primal violence. He's apparently one of the beings who can call up and lead the Wild Hunt."

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"Gosh, that's flattering," I said. "But you haven't told me a thing about why they might be interested in the Erlking."
Mab pursed her lips. "The being you ask me about is to goblins as I am to the Sidhe. A ruler. A master of their kind. Devious, cunning, strong, and swift. He wields dominion over the spirits of fallen hunters."
I frowned. "What kind of spirits?"
"The spirits of those who hunt," Mab said. "The energy of the hunt. Of excitement, hunger, bloodlust. Betimes, the Erlking will call those spirits into the form of the great black hounds, and ride the winds and forests as the Wild Hunt. He carries great power with him as he does. Power that calls to the remnants of hunters now passed on from mortal life."

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"They need two things to make this godhood thing go," I said. "The Erlking and the knowledge in The Word of Kemmler. If I can deny them either, the whole shebang is canceled."
"You figure out those numbers yet?" Thomas asked.
"No."
"So... what? You going to put a hit on the Erlking to keep him from showing up?"
I shook my head. "Mab gave me the impression that the Erlking was in the same weight class as her."
"She tough?" Thomas asked.
"Beyond the pale," I said.
"So you can't kill the Erlking. What, then?"

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