The War Lord

The leader of the aliens who made an alliance with the War Chief to kidnap humans to participate in War Games was, by most accounts, known as the War Lord. (TV: The War Games, PROSE: Timewyrm: Exodus) Some accounts, however, suggested that his kind were known as War Lords collectively; (PROSE: Doctor Who and the War Games, Timewyrm: Exodus) as such, he was known as the Chief War Lord. (PROSE: Doctor Who and the War Games)

Biography
The War Lord met the War Chief in a Trastevarian jail. The fatally wounded Time Lord regenerated in front of the War Lord and, so as to not appear weak, told the War Lord of the Sisterhood of Karn's Elixir of Life, which was vital to the Time Lords' regeneration process. (PROSE: Save Yourself)

Striking an alliance, the War Chief provided the War Lord and his people with Gallifreyan time technology, developing the SIDRATs. Using the time vehicles, the War Lords abducted armies of humans and put them in a War Game to cull the weak and leave them with an army strong enough to conquer the galaxy. Remaining on the home planet, the War Lord left the running of the scheme to the War Chief and the Security Chief on another planet.

Following the Second Doctor discovering the plan, the War Lord arrived on the planet to deal with matters personally. When the reprocessing machine had been recaptured, the War Lord ordered the Doctor placed in it. As a Time Lord however, the Doctor was able to resist the machine's effects, causing the Security Chief to suspect that the two Time Lords were in cahoots. When the War Lord was brought to the interrogation room, the Doctor pledged loyalty to him.

When the resistance began to thin the War Lords' forces, the War Lord ordered the Doctor to handle the situation, lest they be forced to detonate a neutron bomb. When the Doctor delivered the resistance, the War Lord ordered him to make the reprogramming machine capable of returning the rebels to their complicit state but chose to remain on the planet until the situation was resolved.

The Security Chief then revealed the War Chief's deception to the War Lord. Following the Doctor revealing to the resistance that he'd never defected and forcing the War Chief to stop the fighting, the War Lord confronted the War Chief in the landing bay, ordering his forces to kill the Time Lord. The resistance then arrived in the bay where the Doctor was forced to summon the Time Lords to halt the scheme. While the Doctor fled to the 1917 zone, the War Lord noted to Arturo Villar that the Doctor would soon wish that the Mexican had killed him before the Time Lords arrived.

Brought to Gallifrey, the War Lord was put on trial by the Time Lords and found guilty. Before the sentence could be carried out, the War Lord's troops arrived to rescue him, taking the Doctor, Zoe Heriot and Jamie McCrimmon as hostages. Forcing them into the Doctor's TARDIS, the War Lord ordered the Doctor to take them to Galactic Sector 973 only for the Doctor to activate the lights, blinding the War Lords long enough for them to escape the TARDIS. Following, the War Lord and his troops found themselves bound by a force field. The judges continued with the sentencing and dematerialised the War Lord and his troops. (TV: The War Games)

However, the War Lord was later reconstructed by his people and went to the planet Karn, believing that the Sacred Flame was necessary for regeneration. The Doctor was sent by the Time Lords to stop him, and the War Lord was killed when he fell into the flame. (PROSE: Save Yourself)

Legacy
The War Lord fathered a son, to whom he was almost identical. His son followed in his footsteps as the joint leader of the Black Coven alongside the War Chief. (PROSE: Timewyrm: Exodus)

Alternate timeline
When the Doctor was removed from existence by, the War Lord was able to conquer the entire galaxy with his human army unopposed. (AUDIO: The Light at the End)

Parallel universe
In one parallel universe, the War Lord was accidentally dematerialised by the Time Lords before the full sentence could be read out. (AUDIO: Exile)