The Warrior was the name used by the fifth incarnation of the Doctor from an alternate universe where the Fourth Doctor fulfilled his mission of altering the creation of the Daleks. He was also referred to as "the Doctor that Was" by the Unified Skaroan Alliance. (AUDIO: Aftershocks)
In a version of history, Sarah Jane Smith successfully convinced the Fourth Doctor to go through with destroying the Daleks. After doing so, they and Harry Sullivan tried to escape Skaro with the Time Ring, but both Sarah and Harry were killed by a prototype Dalek, which also shot the Doctor. However, the Doctor was extracted by Narvin just before the blast could fully kill him. Still slowly dying, Narvin provided the Doctor with the last Elixir of Life of the now destroyed Sisterhood of Karn, triggering the Fourth Doctor's regeneration into the Warrior.
As the results of the Fourth Doctor's decision rippled through time, the Warrior entered the Time War. He sent two temporal bullets to kill the Sixth Doctor and Peri Brown, who had been deemed temporal "aberrations". (AUDIO: Dust Devil)
Throughout the Time War, the Warrior fought on many worlds, sometimes alongside the Master. However, due to the Time Ring being left on Skaro, the Unified Skaroan Alliance, comprised of the allied Kaleds, Thals, and Daleks, gained control over the Time Vortex and all of time, retroactively conquering Gallifrey and the CIA, effectively winning the war. With the CIA, the Alliance placed the Warrior on trial for genocide, but with the help of the Master he trapped the timeline where the Alliance conquered time within a Carrisent Particum. Upon first regenerating, the Warrior had visions of this timeline, and was unsure if sealing it avoided it or if it was still to come in his future. (AUDIO: Aftershocks)
After many years in the Time War, the Warrior eventually became Lord President. He spent much of his time consulting the Matrix for answers on how to end the war, and became close to his assistant Borusa. On Gallifrey, the CIA established the Difference Office, a branch devoted to studying and preventing paradoxes, particularly those caused by guilt-ridden Time Lords attempting to kill their past selves. The Warrior ordered these Time Lords to be executed. One day, an individual appearing like the Warrior but claiming to be the Doctor gathered the Shobogans and proceeded to attempt to depose the Warrior as President. The Warrior revealed this to be an android created by the Kraal Styggron, who forced Borusa to induct him as President. Styggron captured Romana and took her to inject her with a virus that would kill all the Time Lords. The Warrior used the Relics of Rassilon to atomise the Kraal fleet from Oseidon, and replaced Romana with an android duplicate, stopping the virus and allowing the Warrior to find Styggron's location. Styggron revealed to the Warrior he was actually working for the Alliance and the Daleks, and offered to ally with the Time Lords to end the war. However, the Warrior chose to kill him as vengeance for the death of Borusa's lover Zorcha. (AUDIO: The Difference Office)
Like N-Space's War Doctor, the Warrior had abandoned the name "Doctor". (AUDIO: Aftershocks) He did not have any reservations to kill, and, similarly to the Sixth Doctor, he could be rather brusque when provoked. He carried a strong hatred against the Daleks. (AUDIO: Dust Devil, Aftershocks) After many years in the Time War, the Warrior grew weary but nevertheless remained devoted. (AUDIO: The Difference Office)
The Warrior resembled N-Space's Sixth Doctor, but his attire resembled his N-Space counterpart's war incarnation. The Warrior wore a brown leather trenchcoat and a dark green-brown, double breasted moleskin waistcoat with 10 brass buttons and a fob chain attached to it. (AUDIO: Aftershocks) For neckwear, the Warrior wore a scarf knitted in a burgundy and ivory herringbone pattern. (AUDIO: The Difference Office)