Portal

GLaDOS panics and insists that she was pretending to kill Chell as part of testing. GLaDOS then asks Chell to assume the "party escort submission position", lying face-first on the ground, so that a "party associate" can take her to her reward, but Chell continues her escape.

In this section, GLaDOS communes with Chell as it becomes clear the AI had killed everyone else in the center. Chell makes her way through the maintenance areas and empty office spaces behind the chambers, sometimes following graffiti messages which point in the right direction.

These backstage areas, which are in an extremely dilapidated state, stand in stark contrast to the pristine test chambers. The graffiti includes statements such as "the cake is a lie", and pastiches of Emily Dickinson's poem "The Chariot", Henry Wadsworth Longfellow's "The Reaper and the Flowers", and Emily Brontë's "No Coward Soul Is Mine", referring to and mourning the death of the Companion Cube.

GLaDOS attempts to dissuade Chell with threats of physical harm and misleading statements as Chell makes her way deeper into the maintenance areas. Chell reaches a large chamber where GLaDOS's hardware hangs overhead.

GLaDOS continues to threaten Chell, but during the exchange, a sphere falls off of GLaDOS and Chell drops it in an incinerator. GLaDOS reveals that Chell has just destroyed the morality core or her conscience, one of the multiple "personality cores" that Aperture Science employees installed after the AI flooded the enrichment center with neurotoxin gas.

With it removed, she can access its emitters again. A six-minute countdown starts as Chell dislodges and incinerates more of GLaDOS' personality cores, while GLaDOS discourages her both verbally, with taunts and juvenile insults, and physically by firing rockets at her.

After Chell destroys the last personality core, a malfunction tears the room apart and transports everything to the surface. Chell is then seen lying outside the facility's gates amid the remains of GLaDOS.

Following the announcement of Portal 2, the ending was expanded in a later update. In this retroactive continuity, Chell is dragged away from the scene by an unseen entity speaking in a robotic voice, thanking her for assuming the "party escort submission position".

The final scene, after a long and speedy zoom through the bowels of the facility, shows a Black Forest cake, and the Weighted Companion Cube, surrounded by a mix of shelves containing dozens of apparently inactive personality cores. The cores begin to light up, before a robotic arm descends and extinguishes the candle on the cake, causing the room to blackout.

As the credits roll, GLaDOS delivers a concluding report: the song "Still Alive", which declares the experiment to be a huge success, as well as serving to indicate to the player that GLaDOS is still alive, that her "happy" core was not disabled.