If you are a fan of the original 1993 game Doom, you are in for a treat with Romero Games offering up a new expansion for the original game to celebrate its 25th anniversary. The game is called SIGIL, and John Romero says that the game is a free megawad that contains nine single-player levels and nine deathmatch levels with music by metal

Source: Hot Hardware – Doom Gets 25th Anniversary Mod With 18 New Levels Created By John Romero