From Halopedia, the Halo wiki
For other uses, see Oracle.
Oracle is an achievement in Halo 2 for Windows Vista, and Halo: The Master Chief Collection. In the PC game it is worth 30 Gamerscore and is unlocked by beating The Oracle on Normal, Heroic, or Legendary. In The Master Chief Collection it is only worth 10 Gamerscore, though it can also be unlocked on Easy.