Lucius

Lucius, also known as the Ancient Adventurer, is a recurring character in Pokémon Horizons: The Series. He was a Pokémon Trainer from 100 years ago and one of the Explorers' founders. His legends were also the main reason Roy became a Trainer himself.

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Additionally, Lucius and his partner Rystal are Liko's great-great-grandparents.

(Source: Bulbapedia)