Marcus was a 70's hard driving, 3 guitar juggernaut led by 3 time NBA MVP Moses Malone who...oops, my bad, they were led by Marcus Malone (hence the band name Marcus).  This Malone was once the lead singer for Mitch Ryder and the Detroit Wheels  before forming this band.  They were subsequently signed to the United Artists label with the help of none other than Ike Turner.  The label insisted on some lineup changes (including Cactus' Tim Bogert on bass), which is how they ended up with the unusual 3 guitar lineup.  Their sound has been described as a cross of Aerosmith and Deep Purple and perhaps Angel.  Can't argue with the Deep Purple assessment, particularly on the album opener Black Magic, which begins and sounds just like Space Truckin'.