In Quake, it is known as Nightmare and unlike Easy, Normal and Hard, it isn't found in the first part of Introduction. To find the Nightmare portal, the player must enter any of the portals (doesn't matter which one) and then go to the Episode 4 corridor. Enter the Water and step backwards to put the character's back against the wall behind. After falling through the Water, the player should be on a wooden beam looking down on the gate that leads to the Slipgate. Follow the beam to the corridor in the left hand side and around the corner there is a Lava Teleporter with the word Nightmare written down on both sides.
Nightmare makes the monsters even more deadly, giving them faster reaction times and attacks. For example, the Shambler can now fire its lightning beam twice as fast (and requires you to wait double the time due to an invisible second beam) and Ogres can now launch its grenades at an alarming rate. Vore pods also move at a faster rate, it is impossible to outrun the pod. Enemies cannot be so easily stunned in Nightmare, after the first stun the player must wait five seconds before the enemy can be stunned again.
The community often debates if Hard or Nightmare is the hardest difficulty in Quake. While attacks are more rapid and id Software intended for Nightmare to be the hardest difficulty, Ogres, the most common enemy, are considered by the community to be easier on Nightmare due to the fact that they will constantly be firing at the player. As they don't attempt to close the distance, this means they can be easily killed from a distance or from a raised surface. Other monsters with ranged attacks such as Scrags or Death Knights can be exploited, this behavior means they are more likely to remain stationary, which means it is much easier to Circle Strafe opponents. The lack of movement and the constant spamming of ranged attacks means players will not be surprised with melee attacks, this overly aggressive behavior is considered broken by numerous members in the community due to its more predictable behavior.
Note that it is impossible to reach the Nightmare mode Teleporter via normal means (without using Console Commands) after Episode 4: The Elder World has been completed. This means that it is advisable to play that Episode only after the completion of the other three. As Episode 4 needs to be completed prior to accessing Shub-Niggurath's Pit, this means it is also impossible to change to Nightmare mode before the final level of Quake without the usage of Cheats. Using target lines or an automatically executed configuration, it is possible to set Quake to normally go to a particular difficulty without needing to go through the Introduction level; this functionality is quite useful for custom levels or even commercial add-ons, such as Q2 or Dark Hour, that may not have a built-in method to select difficulty.
Unlike Quake, Nightmare is not a hidden difficulty, instead being marked as one of four routes that the player can choose. With conveniently marked signposts showing the route, it is not hard to find the corridor leading to the Nightmare Teleporter. However, like the base game, each difficulty becomes more of a challenge to access than the one before it; Nightmare can be difficult to reach for the unacquainted player.
Following the corridor leading to the Nightmare Teleporter, the player will find it drops to a lower level. However, between the two corridors is a pit of Lava, sunken enough that is is impossible to escape from when dropped into (at least without a Rocket Jump, conveniently Aftershock does not take away weaponry obtained from past Episodes, nor are they barred off after completion, providing infinite supplies of Ammo for those determined). While a bit of a risky jump, the most lethal element comes without warning, an invisible Wind Tunnel that pushes players into the trap they sought to avoid, the pit of Lava. A near impenetrable wall to break, one that requires a leap of faith, the player must drop to a small extension that exists on the extreme right side of the lower corridor.
The proper procedure for reaching the lower corridor is to head to the end of the corridor and face the dropping point, giving enough room to make a diagonal run across. The player should then move to the left, hugging the extreme left wall. Facing the upper right corner of the hallway, players should run diagonally to it. If properly angled, which leaves the possibility for error if not experienced with movement, they will continue past the wall to reach the outcropping (the Wind Tunnel prevents moving too far forward, while the walls of the corridor do not stretch as wide as the extensions below). The Nightmare Teleporter is at the end of the small corridor after the drop, just out of sight from the upper level. While Quake retains the difficulty between Episodes, meaning the player starts in the Episode selection section, Aftershock differs in the fact that it requires the player to navigate the Difficulty selection section upon every return. This means the aforementioned procedure must be done multiple times if the player wishes to play multiple Episodes on Nightmare difficulty.
At the beginning, go through the hallway marked "Normal". Continue on until you reach the room with the Normal difficulty slipgate in it. Instead of going through, take the hallway to the left. Eventually you'll find a large pile of crates. Climb onto it and you'll find a hidden elevator. Take it and you'll find the slipgate that leads to Nightmare.
To access DoE's Nightmare, you need to activate three buttons. Enter any of the difficulty portals. Walk forward until you're at the entrance of the two episode selection rooms. Go around the wall on either side to see a small area with a lamp hanging from the ceiling. There is a button next to the lamp on both of these sides. Shoot them both. Now find the portal that takes you back to difficulty selection. Shoot into it and you'll trigger the third button. Go back to where you teleported in (marked by a square tile) and look up. You should see a tunnel in the ceiling filled with lava. Stand under the tunnel in a certain spot and an elevator will raise you into it. You will be teleported into a room containing the portal that takes you to Nightmare.
In Quake II, Nightmare is renamed to Hard+. To play Hard+, go to the console and type in "Skill 3" (Easy=Skill 0, Medium=Skill 1, Hard=Skill 2, Hard+=Skill 3) and then type "Map base1". This will start the game from the first level on the difficulty level. Hold F1 to see the objectives and in the top right hand corner, it will say which difficulty is in effect. Trying to start the game like normal from the menu will result in it going back to the difficulty level you chose in the menu. Typing in "Skill 3" will not change the setting until the player starts a new map.
Differences introduced in Hard+ include faster enemy attacks and enemies with more health (one example of this is the Carrier, who has 3,000hp in Hard but 4,000hp in Hard+). But the main difference is that monsters will never go into pain (unlike in Quake 1 where enemies went into pain the first time you hit them). All if not most enemy data on this wiki is taken from the Hard difficulty.
Quake 3 and 4
In Quake 3 and 4, the Nightmare difficulty can easily be accessed from the list of difficulty levels before playing a game. In Quake 3 it is known as Nightmare, but in Quake 4 it is called General, as the difficulty levels are named after military ranks as opposed to Easy, Normal, Hard.
- The demonic groan heard when selecting "nightmare" mode in Quake 3 Arena is a sample of a woman moaning, played at 1/4 the original speed.
- In the first Quake, some enemies have difficulty aiming at the player in Nightmare difficulty. Ogres have been noted to lob grenades haphazardly without accounting for the player's altitude, and Shamblers can be tricked into getting stuck in a melee attack animation.