Quake Cheats

Go to the Episode 4 entrance and jump into the water. Now backup against the wall like you were going to go back the other way. Now stay against the wall and allow yourself to fall down. You should land on a big piece of wood. Walk along the left side to find another entrance that leads a to gate thats takes you to Nightmare Difficulty.

Open the console by pressing the key just left of the ''1'' button on the keyboard; then type ''map x'', where x is any of the following:

start - the introduction level, in which you select difficulty and which episode
e1m1 - The Slipgate Complex
e1m2 - Castle of the Damned
e1m3 - The Necropolis
e1m4 - The Grisly Grotto
e1m5 - Gloom Keep
e1m6 - The Door to Chthon
e1m7 - The House of Chthon
e1m8 - Ziggurat Vertigo (a hidden level)
e2m1 - The Installation
e2m2 - The Ogre Citadel
e2m3 - The Crypt of Decay
e2m4 - The Ebon Fortress
e2m5 - The Wizard's Manse
e2m6 - The Dismal Oubliette
e2m7 - The Underearth (a hidden level)
e3m1 - Termination Central
e3m2 - The Vaults of Zin
e3m3 - The Tomb of Terror
e3m4 - Satan's Dark Delight
e3m5 - The Wind Tunnels
e3m6 - Chambers of Torment
e3m7 - The Haunted Halls (a hidden level)
e4m1 - The Sewage System
e4m2 - The Tower of Despair
e4m3 - The Elder God Shrine
e4m4 - The Palace of Hate
e4m5 - Hell's Atrium
e4m6 - The Pain Maze
e4m7 - Azure Agony
e4m8 - The Nameless City (a hidden level)
end - Shub-Niggurath's Pit

For example, type ''map e1m2'' to access the ''Castle of the Damned''.