Portal: Prelude

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Portal: Prelude
Mod Portal Prelude Splash.png

Basic Information
  • Nicolas "NykO18" Grevet
  • Jérémy "Capitaine Mousse" Barbe
  • Marc "Moroes" Bidoul

Source Engine


Microsoft Windows

  • International: October 9, 2008



First-person puzzle/platformer



  • Portal
  • Processor: Intel Pentium 4 3000 MHz
  • Display Card: DirectX 9 compatible graphics card
  • Memory: 1024 MB
  • Free Disk Space: 1.5 GB
  • Operating System: Microsoft Windows 2000/XP/Vista

Portal: Prelude is an unofficial prequel to the game Portal, developed by an independent team of three. The game features a brand new storyline focusing on the pre-GLaDOS era of Aperture Science where test subjects are monitored by employees of the facility. The game spans across 8 chapters covering 19 test chambers which follow a gradual learning curve similar to that of Portal. In addition, 16 challenge maps and 6 advanced test chambers are included with the mod.

Many gameplay elements from Portal make a return in Prelude, while entirely new gameplay devices were created exclusively for the mod, such as localised gravitational fields. Portal: Prelude also features over 400 lines of text to speech, with English, French and German subtitles.

An official remaster titled Portal: Prelude RTX with RTX support, updated maps, and proper voice acting was released on Steam 15 years later on July 18, 2023.


Portal: Prelude opens up on much the same manner as Portal, with the player, Abby, waking up from a brief detention in a Relaxation Vault. The player is greeted by Mike, an overseer of the Enrichment Center, and another employee named Erik.

Shortly thereafter, the player receives a Handheld Portal Device. However, this Portal Gun is not fully upgraded, and, unlike in Portal and Portal 2, can only shoot orange portals. After the player proceeds through a number of tests, he or she receives a Dual Portal Device. The player proceeds through more test chambers, encountering new people and gameplay mechanics, such as Peter and Localised Gravitational Fields. The Weighted Companion Cube also makes an appearance, though like in Portal the player must euthanize it at the end of the chamber. After the player completes the final chamber, they return their device and proceed to their party. However, the party must be delayed because of the activation of GLaDOS. The player gets to watch the activation of GLaDOS. However, its Morality Core was not installed, and so she kills most of the employees in the room. Mike shuts the whole system down, but the auxiliary power will turn on in a few minutes, so the player must quickly find the morality core and install it on GLaDOS. The player finds a new Portal Gun, and proceeds to find the Morality Core. However, by the time they get back to GLaDOS's room, she has already awoken and has started filling the facility with neurotoxin. After evading GLaDOS's traps, the player finally manages to install the Morality Core. However, their effort is in vain, and she continues the attack, she grabs Abby with the anti-gravity force and slams her into a wall, knocking her unconscious and almost killing her.

Abby then briefly wakes up to see a scientist trying to reason with GLaDOS, but is immediately killed with a laser just before she floods the room with neurotoxin. Succumbing to the neurotoxin, Abby blacks out, and awakens to being dragged out of the chamber by a female Aperture Science employee. In the post credits scene, an incredibly weak Abby is seen walking through the parking lot of Aperture Science (where it is now raining), collapsing, and (presumably) dying, as the screen fades to black. The last thing she sees is the G-Man, standing in the booth and adjusting his tie. Her fate is left unknown, although it's almost certain that she dies from blood loss.


  • Portal: Prelude won third place in ModDB's Mod of the Year 2008.[1]


Though other female characters are mentioned, all of the employees the player sees in the mod are men and have nearly the exact same design, excluding the party hats near the end of the game. The only exception is an unnamed female employee wearing a face mask seen dragging Abby out of GLaDOS's room during the ending cutscene.

The G-Man from the Half-Life series is also seen many times in this mod, possibly to warn Aperture Science of "unforeseen consequences".

External links