Plenty of people have offered their opinions on the Promethean works leading up to the high difficulty / slaughter genre but Hell Revealed is the big one. It ultimately served as a monograph that crystallized notions about the style, establishing a baseline for future experimentation. The first big wave of HR progeny was largely Scandinavian in nature and took several different routes. This resulted in 2001 / 2002's Alien Vendetta (organized by Anders Johnson); 2003's Hell Revealed II (largely characterized through Jonas Feragen's work); and Erik Alm's run from '01 to '03, culminating in Scythe. Adolf "Gusta" Vojta's Kama Sutra, a full Doom II megaWAD released in 2005 with some assistance from Jakub "Method" Razák, is a synthesis of all these influences.
