Brisingamen — Diana L. Paxson

Imagine that a shy graduate student has discovered the legendary necklace Brisingamen -- whose wearer bears the powers of the goddess Freyja, mistress of love and war...

Imagine that Freyja's enemy, Loki, has come to San Francisco to steal it back, so that he can release his fiery reign of terror...

Imagine that only Karen Ingold can stop him. Together with her unlikely allies -- a one-eyed biker, a red-bearded carpenter, and a spinsterly Tarot reader -- Karen must follow her enemy to a twilit world of myth and magic...not unlike our own!