IdBase

idBase  is a Level Theme in Quake that specifically uses id Software's Base textures. They are usually designed in the theme of a processing station and have giant pools of Slime and/or Water. The metal and concrete is mostly beige or brown/grey to represent a militaristic palette. They also have normal blue skies, which contrast with the purple found elsewhere, and show that these levels are located on Earth.

In the vanilla game, these are the levels that start each Episode. They represent the secret military installation on Earth that was overrun by Quake's forces. Slipgates, man-made Level Exits, are spread throughout the military base. As these were the devices the Enemies used to reach Earth, Ranger was able to travel across the invaded complex with the goal of teleporting to the home dimensions of his foes. From there, he was able to seek out the Runes of magic power at the end of each dimension so that he could reach Shub-Niggurath through the combination of their power.

John Romero was responsible for this theme, attempting to use it to make a cohesive narrative that would explain the extremely different Level Themes found in Quake.

The prior occupants have been rewired, leaving them with the sole purpose to kill all intruders. Soldiers have been turned into Grunts, Shotgun wielding undead. The Grunt does exist in E1M2: Castle of the Damned, though is found most commonly in idBase. Fighting alongside the Grunts are the Rottweilers and Enforcers, neither of which are seen outside of the idBase levels.

Radioactive Containers, metallic boxes with unstable elements that explode on contact, are littered across the processing station. Futuristic defense systems such as the Laser Traps slow down the progress of intruders. Computers are piled on top of one another, chirping as they carry out unknown processes. Crates have been placed in close proximity to the Slipgates for easy transportation to the dimensions beyond. Being set in a futuristic world, the Key used to unlock Doors appears to be a thin keycard.

Levels

 * Introduction - Merged with Wizard, Terracotta, Elder World, and Runic.
 * E1M1: The Slipgate Complex
 * E2M1: The Installation
 * E3M1: Termination Central
 * E4M1: The Sewage System
 * DM3: The Abandoned Base