The Gestalt pilot and officer of Penrose-512. After their ship crashlands on the frozen planet Leng, her Replika crewmate Elster goes in search of her throughout Sierpinski.
It's eventually revealed that Ariane and Elster are lovers, and that Elster's search for Ariane is to fulfil an unknown promise the two of them previously made onboard the Penrose.
It's additionally revealed that Ariane is Bioresonant, and heavily implied that much (if not all) of the games events and story are caused by her bioresonant abilities.