The first thing the Agalloch frontman John Haughm does at the beginning of concerts is light incense at the foot of the stage.

For almost two decades, Agalloch has been honing a naturalistic stripe of metal — thoroughly meditative, verging on yogic at times.

“The Serpent & the Sphere” is perhaps a notch off Agalloch’s peak: transcendent, darkly beautiful albums like “Ashes Against the Grain,” from 2006, and “Marrow of the Spirit,” from 2010.

Aloes: the fragrant resin of the agalloch or lign-aloe of Scripture.