By MARC WEINGARTEN

Even if Fleetwood Mac hadn't enlisted the services of Stevie Nicks in the mid-'70s, you somehow get the feeling she would have become a rock icon anyway. That band may have produced hits from three different singer-songwriters, but when it came to filling arenas, it was Nicks, the pagan goddess of the L.A. music scene, that fans came to see. That mystic-chick persona remains a powerful lure for Nicks' fans. On Monday the singer had the Universal Amphitheatre stage festooned with pink drapes and a giant stained-glass backdrop, and appeared in a seemingly endless series of flowing dresses and diaphanous shawls. Nicks was every inch the seraphic diva, her patented whirling dervish dance eliciting huge roars from the crowd of adoring supplicants. In contrast to her output with Fleetwood Mac, which tended toward genteel folk-rock, Nicks toughened up her sound for her own albums, juicing her material with blustery guitars and big, radio-ready keyboards. At the amphitheater, Nicks went with a two-guitar, two-keyboard lineup, and attacked up-tempo rockers such as "Stand Back" and "Edge of Seventeen" with the kind of unforced urgency that was missing from last year's too-polite Fleetwood Mac reunion tour. But sometimes being in a band provides the checks and balances that are necessary to avoid self-indulgence. On Monday, Nicks paused for an acoustic mini-set that laid bare her penchant for flowery metaphor and clunky, pastoral imagery. And there were countless annoying pauses for the costume changes that gave the show a Vegas taint. Nicks' voice has lost none of its range or quirkiness; she thrilled the crowd whenever she used her craggy vibrato to stretch out a melody line. Her Gypsy Queen dance steps have grown tired, however, and have merely become a means to milk the crowd. No matter; what Nicks lacked in spontaneity she made up for in show-biz spunk and polish.