Ghost October 31, House of Blues.

There’s no better way to spend Halloween than watching an opening act named for one of the kings of Hell, and a headliner that worships all of them.

First, London-based Purson kept House of Blues’ dementedly costumed crowd moderately entertained with 40 minutes of vintage rock ’n’ roll, but the highlight of the set came as the five-piece exited the stage. Theatrical Swedish metal outfit Ghost immediately began exercising its mastery in setting a dark mood, as a backdrop of stained-glass church windows illuminated blood red while thin fog and faint choir music filled the front of the venue. As the horn-masked band of “nameless ghouls” eventually emerged one by one, an imagery that can come across as trite in the band’s recorded output felt more effective brought visually to life.

The two guitarists and bassist traversed the stage around their skeleton-faced, vestment-clad vocalist, Papa Emeritus, as if possessed by a higher, er, lower power. The demonic dance-team movements provided ample room for Emeritus, who spent most of the night with his arms outstretched as if he were satanically blessing the crowd. But Emeritus never let the theatrics, which included swinging a thurible to spread incense, overshadow his eerie and oddly cozy voice while the band burned through a 17-song set drawing heavily from this year’s Meliora.

Emeritus also delivered sermons on vampirism, cannibalism, carnality and avarice to the captivated congregants between songs. Much like Halloween itself, Ghost is a mostly silly idea that’s fun enough to observe annually.