Halloween Costume How-To: Slay Demons As A 'Mortal Instruments' Shadowhunter

You know what's truly scary? Waking up October 31 without a Halloween costume and—gasp!— having to settle for a five-sizes-too-large sexy hedgehog outfit from Spooky Central. Which is why we're getting an early start at Hollywood Crush prepping the perfect pop-culture costumes.

"The Mortal Instruments: City of Bones" film may not hit theaters until August 2013, but why wait until next year—when everyone else will be dressing as a demon-destroying Shadowhunter—to break out your black? Be a trendsetter! Here's how you can slay as the fierce Nephilim from Cassandra Clare's best-selling novels.

"Looking Better in Black" isn't just a slogan for the Shadowhunters—they wear the midnight hue with aplomb while fighting the world's foes. Even better? All of these black basics can be purchased at Forever 21 (and for relatively little green!). Start off with a pair of Pintucked Moto Jeggings (complete with awesome ribbing detail) for only $19.80, then top with a flesh-flashing basic tank (revealing plenty of surface area to display your runes). Add a pair of Isabelle-approved booties (we like this pair of lace-ups) or, if you prefer comfort over couture, combat boots sans heel will also do the trick. Finish with a slick jacket (like this Faux Leather Peplum one for $34.80).

A Shadowhunter is nothing without her runes though! Buy a kohl eye pencil or black lipstick to draw the protective markings on your arms and other visible areas of skin. Cassie's website has a full array of designs for you to crib, or you can always make up your own.

The final touch is your stele—that magical tool used to draw Shadowhunter runes. For an easy, homemade solution, grab a twig off the ground or bunch together a couple of pipe cleaners and wrap in aluminum foil. And—voila!—you're ready for any Magnus Bane Halloween party!

Will you be dressing as a Shadowhunter this Halloween? Tell us in the comments and on Twitter!