Caitlín R Kiernan's four-page Alabaster: Shelter story will be spread across the two issues.
Based on the writer's Dancy Flammarion stories, Alabaster: Wolves debuted last week in Dark Horse Presents #9.
The series centres around Flammarion, a seventeen-year-old girl who hunts monster and demons at the behest of her terrible angelic guardian.
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Alabaster: Shelter will be featured in the FCBD Star Wars/Serenity and Buffy/The Guild flip-books at the event in May.
FCBD is held on the first Saturday of every May for publishers to promote their comics to new readers.
Last year's event broke records, with over one million people estimated to have visited a comic book shop and 54% of stores reporting increased profits compared to average Saturday takings.
Free Comic Book Day 2012 will be held on May 5 this year.
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