"I'm lonely, you're dry on ammo, we can help each other"
-Advertisement for The Trader
The Trader is a mysterious woman who sells an arsenal of military grade, as well as improvised, weapons to those who are fighting the war against the Specimens. Not a lot is known of her background before the outbreak, but her shops usually contain newspaper clippings that suggest that she has been closely following what has been going on. She tends to flirt with the player quite a bit, and is one of the few characters with unique voice samples.
She advertises her store though signs scattered around the levels. Her barricaded store, which changes location after each wave of enemies, temporarily opens once the player(s) have killed all the mutants outside.
During the "Potato Fool's Day" Alternate-Reality Game (ARG), The Trader was replaced with GLaDOS.