It was the perfect day in Equestria. The sun was shining brightly, the ponies blissfully lazing through their daily routines. That is, until GLaDOS appears.

Destroyed by Chell on Earth, GLaDOS now finds herself in Equestria, in a brand new body. One that is far more powerful than her previous one. She then kindly introduces everypony to her old friend, deadly neurotoxin.

[Takes place after Portal 1]