She was a ranger, who protected a lake, which contained a crystal that healed Electric Pokémon. When Ash's Pikachu got hurt, she took the heroes to the lake, where Ash placed Pikachu, who was healed. When Team Rocket stole the crystal, Zapdos appeared and blasted them off, but injured itself as well. Krystal watched over Zapdos, until the heroes came. Ash placed the crystal back and with the Electric Pokémon's help, including Zapdos', the crystal worked again. Krystal was grateful for assistance, while the heroes promised they wouldn't reveal anyone the secret of the lake.
Krystal took care of Zapdos, who got exhausted and injured in the fight against Team Rocket.