“There is still more Science to do, isn't there? That was rhetorical, before you work up your lungs for a half-baked response. Of course there is. There always is.”
—GLaDOS, DTG2: One Year Older
GLaDOS is the main antagonist of Portal and a recurring antagonist in the Destroy the Godmodder series. She is an artificial intelligence built to control the laboratories of Aperture Science. Her body was used by the Advanced Superiors as the template to build Project Binary. In Destroy the Godmodder, She was summoned as an entity by TwinBuilder and later joined the Counteroperation in Destroy the Godmodder 2.
GLaDOS was apparently, along with the rest of Aperture Science, built in Upper Michigan on Earth in Universe B. It is unknown exactly how GLaDOS can exist in Her current state if the events of Half-Life obviously didn't happen in Universe B. The events of both Portal games passed before the Godmodding Wars.
GLaDOS first interacted with GenericCraft and Destroy the Godmodder when TwinBuilder drove to Upper Michigan and confronted Her. It seems that She has known him for a while, because he is able to convince Her to give him the Turret Army in exchange for some reserves of deadly neurotoxin. Once the Turret Army is destroyed, GLaDOS summons Herself to the Battlefield.
Since Her alignment is undetermined, players had to bribe her to a side. The Anti-Godmodders eventually won out and She fought for them using deadly neurotoxin, but was destroyed by the Glitch. It seems that Her body on Earth remained intact, and was idle during the remainder of DTG.
A copy of GLaDOS was resummoned by the Godmodder in DTG2 thanks to the Wayback Machine. However, this seems to have no bearing on GLaDOS' current state on Earth. Her relations with TwinBuilder have grown hostile, and She now resented him for destroying Her Turret Army and inadvertently destroying Her as well. She also seemed to figure out various things about the war in GodCraft, such as the fact that TwinBuilder is now the First Guardian of Minecraft.
Eventually, Aperture Science received new visitors as the Advanced Superiors of MTT Industries used GLaDOS' technology, the research of Aperture Scientist employees, and a slew of new employees, to construct Project Binary. GLaDOS became a part of the Counteroperation's special ops team as a result. It was Her job to create a portal powerful enough to breach a hole through the Narrative and enter GodCraft itself. She did this by extracting the Godmodder's code and reverse-engineering Tabletopian chronal technology.
Once the Arrival fleet congregated at Aperture for the last time, which has served as the special ops' base of operations, Bill Cipher activated the portal and the fleet passed through it and into GodCraft. GLaDOS, who cannot move from Aperture, sended a hard-light avatar containing Her essence into the portal, effectively creating a copy of Her. She proceeded to attack the forces of GodCraft upon Arrival, fleeing with the rest of the special ops as the Glitch took over once more. She then waited for the players, and, once they arrived at the Descent, fought against them.
Despite fighting against the players, GLaDOS was ultimately killed by the Godmodder, whereupon Netpatham claimed a Hard-Light Gun as a Spoil of War from Her. Since this is only GLaDOS' hard-light avatar, GLaDOS' real self remains intact in Aperture Science, where she has remained since.