In The Elder Scrolls IV: Oblivion, the traitor within the Dark Brotherhood is Mathieu Bellamont.

Quick Scoop

  • The Dark Brotherhood traitor’s name is Mathieu Bellamont.
  • He is revealed near the end of the Dark Brotherhood questline, after a series of “dead drop” contracts that secretly manipulate you into killing members of the Black Hand.
  • His motivation is personal revenge: Lucien Lachance ordered the killing of Bellamont’s mother years earlier, which drove him to infiltrate and sabotage the Brotherhood from within.

How the Betrayal Unfolds

  • After the Purification of the Cheydinhal sanctuary, you start getting contracts through dead drops, but these are actually altered by the traitor so you unknowingly assassinate Black Hand members.
  • The Black Hand blames Lucien Lachance and tortures him to death, believing he is the traitor.
  • By tracking the false dead drops to Anvil’s lighthouse and reading the traitor’s journal, you learn of a vengeful assassin whose mother was murdered by the Brotherhood.

Final Reveal (Spoilers)

  • At Applewatch and then in Bravil, during the “Honor Thy Mother” sequence, the Night Mother is summoned and it is finally exposed that Mathieu Bellamont is the one who has been undermining the Dark Brotherhood.
  • You confront and ultimately kill Bellamont, ending his plot to wipe out the Brotherhood and avenge his mother.

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