Description
Lillie emerges as a pivotal character linked to the Aether Foundation and Lusamine's daughter. She flees Aether Paradise while protecting the Legendary Pokémon Cosmog, affectionately named Nebby, seeking refuge with Professor Kukui as his assistant. Her initial design displays platinum blond hair in twin braids, a white dress with transparent outlines, a large blue-ribboned hat, long socks, ballet-style shoes, and a distinctive round Poké Ball-patterned bag—an outfit selected by Lusamine that mirrors the Ultra Beast Nihilego, reflecting her mother's fixation.

An unexplained childhood fear of physical Pokémon contact, rooted in an Ultra Beast encounter, causes her to freeze or recoil near Pokémon, requiring protective gear for riding. She gradually overcomes this phobia through bonding with Snowy, her Alolan Vulpix hatched from an egg. Milestones include touching Ash's Pikachu without hesitation and riding Stoutland. Recovered memories of Silvally saving her during the Ultra Beast incident fully resolve her fear, enabling free interaction with all Pokémon.

Her family dynamics involve a close childhood bond with brother Gladion, later strained by his departure to gain strength against Ultra Beasts. They reconcile while searching for their missing father, Mohn. Lillie and Lusamine share a tense relationship due to Lusamine's controlling neglect, exemplified by forcibly evolving Lillie's Clefairy into Clefable. Confronting Lusamine in Ultra Space, Lillie declares children are not possessions. Their relationship heals after Lillie rescues Lusamine from Nihilego, and they collaborate to find Mohn.

At Poni Island's Altar, she plays the Sun Flute to evolve Nebby into Solgaleo or Lunala, enabling Ultra Space travel to confront threats and rescue Lusamine. Her growing confidence and decision to become a Pokémon Trainer are marked by an outfit change: a white sailor-style shirt, light blue-lined miniskirt, pink backpack, and ponytail secured with a braid. She inherits her father’s white Z-Ring with a red strap, using it for Ice-type Z-Moves.

Lillie journeys with her family to Galar's Crown Tundra, discovering Mohn amnesiac and living with a shiny Nihilego he believes is his daughter. Friends help restore Mohn's memories via a mirror, reuniting the family. Lillie thanks the Nihilego for caring for her father and invites it to Alola. Her story concludes as a determined Pokémon Trainer, aiming to challenge Gyms and encounter diverse Pokémon across regions.