Just a Touch of Kleptomania

(Dumbledore Bashing! Lunar Harmony!) Based on, but not an answer to DZ2's "What's Yours is Mine" challenge. The Shadow-Walkers, magical thieves of extraordinary power, have long been thought extinct. But Harry, Hermione and Luna not only have those powers, but intend to use them to take everyone from Dumbledore to Voldemort to the cleaners...and make a little profit along the way.