With dragon-throated Ronnie James Dio fronting Ritchie Blackmore’s band for the last time, this 1977 album capped Rainbow’s classic period, laying the melodramatic groundwork for ‘80s power metal. Its structures bridged the prog of yore (“Gates of Babylon” navigates all over some mystic map and climaxes in a sumptuous solo) with the thrash to come (“Kill the King” makes heads roll at a breakneck tempo). A crucial link between Led Zeppelin and Iron Maiden, this album is an utterly majestic step in metal’s evolution.