Doom Bible

The Doom Bible is the original design document for Doom, written by Tom Hall.

Some bits and pieces from the Doom Bible show up in various places:
 * The prefixes TROO, SARG, and BRS on IWAD lumps for the Imp, Demon, and Baron of Hell come from their Doom Bible names: Demon Trooper, Demon Sergeant, and Bruiser Brothers.
 * The Unmaker appeared in Doom 64.
 * Out of all the proposed episode names, Knee-Deep in the Dead is the only one that made it into the final game. It was originally to be the third episode out of six.
 * The game originally took place on a planet called Tei Tenga. If you look close at some of the computer panels in Doom, you will see that they still say "UAC BASE TEI TENGA" on them.
 * The game Terminal Velocity also featured a planet called Tei Tenga.
 * All of the playable characters in Rise of the Triad had origins in the Doom Bible. Some of them had their names altered, and one only appeared as a possible name, but a one or two were unchanged from how they were originally described.
 * In Strife, there is a place where the player uses a severed hand to unlock a door. This was also proposed in the Doom Bible.  Maybe this is a coincidence, or maybe not.