"Search the waste for the Cartographer."
The Ark is the seventh campaign mission of Halo 3.
It takes place in a desert that comprises one of the center-most regions of the Ark, located 218 light-years outside the Milky Way galaxy's center.
In this level, the Covenant Separatists and the Humans side with 343 Guilty Spark and his Sentinel allies to access the Cartographer and find The Prophet of Truth.
Beating this mission on Heroic unlocks the Shoulder Pads to the Elite Flight Harness Armor Permutation.
Beating this level on Normal unlocks the E.V.A. shoulder pads. Beating this level on Legendary gets you the E.O.D shoulder pads