Underneath his mysterious metal mask, MF DOOM hides the cachet underground legends are made of. After his first group KMD’s sophomore album Black Bastards was shelved by Elektra in 1994, and his blood brother Subroc — one half of the sibling rap duo — passed away, surviving frontman Zev Love X slowly mutated into the supervillain MC known as MF DOOM, and the rap world is better for it.

The 1999 release of Operation: Doomsday marked MF DOOM’s official debut, reintroducing a mysterious figure who would soon become one of underground rap’s greatest voices. Within its 19 tracks, Operation: Doomsday reveals the confluence of DOOM’s tragic past, personal interests and daring creativity. His clever rhymes and remarkable schemes stood out against the landscape, and every sound he touched —from cartoon theme songs, to ‘80s soul, to rap classics and more — got reinterpreted into something brand new and surreal.