Indie rockers deepen their commitment to stoner metal, get inspired by Carl Jung, and pen lyrics about swashbuckling travelers and the risen dead? The Gathering should be a hoot, at the very least, but this Baltimore clan’s fourth release is more of a slog, shackled by monochromatic guitar churn and a slack pulse. Sure, Arbouretum singer-guitarist Dave Heumann leads us on a journey through his sun-scorched psyche, but it’s a trip with few highs or lows save for intermittent instrumental heroics. When the nearly eight-minute, Tool-like “Waxing Crescents” manages to dim the palette from brown to black,it’s a serious shift.