See how often they participate in the script: HERE.
Character Story: One of two Yetis that Link meets. Yeta is suffering from a sickness that owning a piece of the Twilight Mirror, the entrance to the Twilight Realm, has brought upon her. Link helps to heal her in exchange for the Mirror Piece.
Race Story: The Yeti live in a very private, frozen region in Northwestern Hyrule that is distantly connected to Zora's Domain.