H. P. Lovecraft

Howard Phillips Lovecraft (August 20, 1890–March 15, 1937) was an American author of fantasy and horror fiction, whose work influenced Doom (and also Quake) significantly. In particular, Sandy Petersen is a big fan of Lovecraft.

Specific references include:
 * The name of the Cacodemon may have been taken from the sentence "I have said that the fury of the rushing blast was infernal - cacodaemoniacal - and that its voices were hideous with pent-up viciousness and desolate eternities." from The Nameless City