All-star jam band Royal Machines is already made up of some seriously amazing musicians, but during a Hollywood gig on Dec. 19, a metal icon joined the act for a song. The Prince of Darkness himself, Ozzy Osbourne, stepped onstage to sing 'War Pigs' and 'Crazy Train' with Royal Machines.

Royal Machines was created from the ashes of Camp Freddy. Featuring Dave Navarro (Jane's Addiction / Red Hot Chili Peppers), Billy Morrison (the Cult), Donovan Leitch (son of folk legend Donovan) and Chris Chaney (Jane's Addiction), the Royal Machines lineup invited Mark McGrath (Sugar Ray) and Adrian Young (No Doubt) to play the Dec. 19 bash.

To see that sort of lineup at a venue like the Roxy is pretty special, but to witness Ozzy Osbourne sing in any place smaller than a coliseum is like finding the holy grail.

The Roxy crowd went nuts for Ozzy, even with during the intro of 'War Pigs,' which moves slightly faster than a snail's pace. 'Crazy Train,' which always gets a crowd moving, brought the same energy out of the audience while Ozzy dumped his trademark bucket of water over those in front of the stage. Props to Dave Navarro as well, who nailed the song's immortal solo penned by the late Randy Rhoads.

Check out Ozzy jamming with Royal Machines in the clips above and below!

Royal Machines with Ozzy Osbourne Perform 'Crazy Train'

10 Unforgettable Ozzy Osbourne Moments