Rockstar Energy Drink Mayhem Festival has diminished, but is still rocking on

There is an inescapable survivor's mentality hanging over this year's Rockstar Energy Drink Mayhem Festival.

The eighth annual touring heavy metal festival is noticeably diminished from past years, with three or four stages reduced to two. This year's headliners both recently emerged from difficult periods. Danish singer King Diamond, 59, underwent triple-bypass surgery in 2010 following several heart attacks, while Slayer has regrouped following the death of founding guitarist Jeff Hanneman and the firing of drummer Dave Lombardo.

So it felt like a rallying cry for the faithful when Hellyeah front man Chad Gray asked the audience at the Susquehanna Bank Center on Friday if they were willing to "bleed for this music."

Given the sparse crowd, that may not be enough. Those who were there, however, were thrilled by two strong sets by metal legends who appeared undiminished by recent troubles.

King Diamond's demonic falsetto and guttural growl were in fine form as he prowled a stage made to look like a cursed chapel, complete with inverted crosses, glowering gargoyles, and a goat-headed, red-lit pentagram. With his black-and-white face paint and microphone mounted to a cross made of bones, King has the air of a late-night horror host, supplemented by the theatrics he brought.

During a brief set of songs from his 1988 concept album Them, which told the story of a young King, his evil grandmother, her minions, and cursed tea, "Grandma" was wheeled on stage.

Since their founding in 1981, Slayer has risen to become - as Hellyeah's Gray said earlier in the night - "the undisputed champions of heavy metal." Their powerful sound was tight and ferocious throughout a merciless barrage of favorites from their 30-plus-year career. A wall of flames, fireballs, or flame-jet inverted crosses stood in front of a video screen of animations illustrating the band's usual dour obsessions: war, religion, and plenty of blood.

Gray's impassioned metal cheerleading for the genre drove Hellyeah's set. The supergroup, which features members of Mudvayne and Nothingface, is powered by former Pantera drummer Vinnie Paul's Texas boogie-fueled grooves, but the band's emo-metal was otherwise distinguished mainly by extreme volume. The main stage kicked off around 6 p.m. with metalcore outfit the Devil Wears Prada, which played a spirited set to a near-empty arena. The second stage launched the day earlier with sets by Code Orange, Shattered Sun, Sworn In, and Sister Sin. Australia's Thy Art Is Murder was the best of the bunch, with its precision riffs and front man Chris McMahon's throaty growl.