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Sierra is a minor character in Kingdom Hearts Legacy.
Sierra appears in Shrine City, summoned by Professor Elica to defeat Troisnyxetienne in a musical battle, to show Troisnyxetienne that her musical abilities are inferior. Sierra defeats Troisnyxetienne, which deeply upsets Troisnyxetienne. She runs off, until she is kindly approached later by Sierra. After this, she can be found walking about in the Indoor Practice Field. Talk to her, and you will receive a Hi-Ether.