The title of Fern Knight’s 2006 release, Music for Witches and Alchemists, served simultaneously as a wonderfully apt description and an unambiguous product warning. If you prefer the mundane to the magical, move on: These are not the druids you’re looking for. Since then, the group has relocated to Arlington from Philadelphia, and while Fern Knight’s music evokes far-away times and places, it turns out the band fits in nicely with the D.C. area’s musical history—assuming you can stomach a medieval-minded, tarot-themed concept album and a frontwoman who seems to shop exclusively at Stevie Nicks’ Boutique of Bewitchery. The group’s self-defined “doom folk” has much in common with D.C.’s doom-metal luminaries—from Pentagram’s dark atmosphere and emotional minor chords to Scott “Wino” Weinrich’s fascination with secret societies and ley lines. Hints of psychedelia, meanwhile, recall the music of Doldrums, Pelt, and Flying Saucer Attack, all veterans of Fairfax-based VHF Records, to which Fern Knight is signed. Margaret Ayre’s dulcet voice is the main attraction of Castings, the group’s fourth record, but her husband Jim’s rumbling electric guitar work balances out the sound, especially on the opener “From 0 to ∞.” On “Pentacles,” Jim’s piercing note progression could be Aliens-era Roky Erickson. Margaret, too, has plenty of tricks up her billowy sleeve—she substitutes her cello for her vocals on the gorgeous instrumental “Cave of Swords.” Castings’ lone cover, a take on King Crimson’s “Epitaph” from In The Court of the Crimson King, is a fine choice for several reasons. First, it’s a deep cut from a prog-rock classic. That, and Fern Knight’s grounded version fits in seamlessly with Castings’ other tracks and with the album’s destiny-pondering themes. On “The Poisoner,” one of Castings’ stronger efforts, Jesse Sparhawk and James Wolf create a tension with harp and violin that manages to sell the drama of Margaret’s lyrics: You won’t even snicker at the line, “Shrouded in black tapestry/holding a dove to my breast.” The real trick to this immersive medieval music is that Fern Knight plays it straight-faced. Hence recording the album in an old Gothic mansion in the dead of winter, and posing for publicity photos with dead-earnest looks while seated at a candlelit banquet table. It doesn’t matter that the name, Castings, sounds silly, like something an incontinent wizard would leave behind in an enchanted forest. Fern Knight has the strength of its convictions and, as a result, sells as beautifully transportative music what in less-serious hands could never leave the ren-faire circuit.