“I’ve got a secret for you,” Dani Neff teases over the deep-cosmos throb of “Keep Learning the Same Thing.” Spoken like a true mystic. Welcome Home, Megafauna’s fourth LP, finds the Austin heavy-psych trio plunging deeper than ever into the ethereal. The wicked rhythms of bassist Will Krause and drummer Zack Humphrey often veer toward Sabbath-styled proto-metal, and Neff—the band’s singer, guitarist and chief songwriter—follows suit with brutal distortion on barnburner mini-epics like “Panpsychist.” Megafauna stroke that sludgy sweet spot throughout while never sacrificing dynamics or tonal variety. The songs ebb and flow between brute force and serenity, building stoned atmospheres laced with hellfire. “Gaia” exemplifies the contrast, as coiling blues-rock riffs collide with feathery, delayed arpeggios; “Desire” lurches around in a fog later punctured by rippling Hammond organ and a guitar solo that conjures Jack White via the noisiest corners of Santana’s Abraxas. “Welcome home; we won the war,” Neff declares on the closing, slow-burning title track. After 40 minutes of interstellar battle, she’s earned the bragging rights.