Landfall (achievement)
From Halopedia, the Halo wiki
Landfall
Landfall is an Achievement for Halo 3 on the Xbox 360.
It is earned when one completes the campaign mission Sierra 117 on the Normal, Heroic, or Legendary difficulties. This achievement is worth 20 Gamerpoints.
It is represented by a blue plate with a roman numeral "I" on it.
Note: You must complete the whole level through from the start, a halfway rally point will not count.
References