Guardian of Chaos - Michelle Manus

Nyx Fortuna never intended to become the Guardian of a Waystation between worlds, but with no job and nowhere to live, disappearing into a place that's not quite Earth doesn't seem like a bad idea.

Nyx has barely rubbed the shine off her new Guardian tattoo when the All-Council-the galactic governing body of the magical universe-informs Nyx that an illegal traveler came through her Station, and it's her job to apprehend him. Her backup? The Station's Avatar-a smart-mouthed, pocket-watch-toting, housecat-sized griffin-and Nyx's new assistant, a rough-and-tumble Amazon who's up to her sword hilt in weaponry.

Things start looking up when the illegal traveler turns himself in, until Nyx learns he actually came to Earth looking for her. He thinks his best friend-and coincidentally Nyx's ex-boyfriend-hid the most powerful object in the universe with her: the Harvester of Worlds. Nyx is determined to sort out this intergalactic mess and keep her new job, even if she has to visit the most dangerous planet in the galaxy and rescue her ex-boyfriend to do it.

Oh, and if she suspects she's been wearing the Harvester of Worlds as a necklace for the last five years, well, what's the worst that could come from a power object with a name like that?