The original Underworld, released six years ago, introduced a high-concept/low-excitement war between vampires in fetish gear and videogame-caliber werewolves — and "in the spirit of equanimity," someone wrote at the time, "the movie both sucks and bites." No such draw here: This deadly prequel explaining the roots of the bloodsucker-fangface grudge match is a 92-minute detainment in Sucksylvania. Like the first two movies, it's too glum and humorless to wring any fun from its dorky premise: At least seven-eighths of this one takes place in a dreary, monochromatic castle, and much of that is in a dungeon. Though he is chained up with other "lycan" slaves, werewolf messiah Lucian (Michael Sheen) pursues a love that dare not howl its name with vampire princess Sonja (Rhona Mitra), while her aristocratic dad, Viktor (Bill Nighy), skulks around like a Balkan Ming the Merciless. In lieu of advancing a story, the third Underworld repeats incessantly — multiple bloody floggings, multiple captures, multiple trudges back to the dungeon — while the cinematography does its best to evoke the many-hued visual splendor of an ashtray. Mincing around like a bored old glam rocker and hissing threats from behind neon eyes, Nighy seems to be the only person on set who found a glint of amusement in his part. He fares better than poor Sheen, a scraggly Wolverine who made a more credible vampire-slayer opposite Frank Langella's Nixon.