HeXen

HeXen actually began development as an expansion for Heretic and was slated to hit the shelves as Heretic II. But the game design expanded far beyond what was originally intended, so it became HeXen: Beyond Heretic. Developed over an 8 month period, HeXen introduced the 'hub system' of level progressions, rotating polygonal brushes and multiple character classes that were available in both single and multiplayer. The game went on to surpass Heretic as Raven Software's most popular title for that time.