Death's Champion

Death's Champion was the title that the Eternal Death bestowed on those who agreed to become her champion.

In the Doctor's youth, he killed Torvic and felt immense guilt. When Death came to him at night, he made a deal so he could forget his crime in exchange for his friend, the Master, becoming her champion. The Master then left Gallifrey and spread horror and death wherever he went. (AUDIO: Master)

The Valeyard warned the Sixth Doctor that, in the coming conflict, Death would choose a champion to face Time's. (PROSE: Millennial Rites)

After the Seventh Doctor became Time's Champion, agreed to become Death's Champion in an attempt to stop him. (PROSE: No Future)