Quiet is a Buddy in Metal Gear Solid 5: The Phantom Pain. She is Metal Gear 5's primary female protagonist and fights alongside Snake throughout much of MGS 5.
She is a sniper with extraordinary mobility and stealth powers. Base level Quiet can scout out encampments, or take attack positions overwatching bases from the mission map. She will intervene if you find yourself in danger of discovery.
Quiet can be upgraded by trust level to take commands, targeting specific foes with the L1 and coordinating with grenade attacks.
Quiet can also upgrade her gear, adding, among other abilities, a non-lethal rifle option useful on Child Soldier missions and for capture.