The addition of Final Doom and Sigil to the Doom 1 and 2 ports is part of a wider initiative by Bethesda to support community-created WADs. Sigil is the nine-episode unofficial follow-up to Doom's fourth level, produced and designed by John Romero, a co-founder of id Software and...
(7) 1.Master Levels/Final Doom: General|Glossary(8) 2.PC Doom II-Based Games: General|Introduction(0) 3.PC Master Levels For Doom II|Master Levels/Final Doom: General(1) 4.PC Final Doom|Microsoft Xbox Master Levels(5) 5.Microsoft Xbox Master Levels|PC Doom II-Based Games: General(2...