Master Chief Mode is available as an optional in-app purchase for the iOS versions of all three games of the Marathon Trilogy. At launch, the price of this add-on was $0.99.
When active, Master Chief Mode has the following effects:
- The game can be started on any level with immediate access to all weapons.
- The game can be saved at any point, without requiring a pattern buffer.
- The player has unlimited ammunition and health (invulnerability) as well as instant shield recharge.
- The infamous Vidmaster Oath will appear in the New Game screen, as well as a Starting Level selection slider.