From Bulbapedia, the community-driven Pokémon encyclopedia.
A Mystery Man (Japanese: なぞのせいねん Mystery Man) is a type of Pokémon Trainer that first debuted in Pokémon Crystal, though it was originally translated as Mysticalman in the English version of Pokémon Crystal. Two important non-player characters have had this class, both of which are, as the name implies, mysterious men. In Crystal Version, Eusine had the title of "Mysticalman", but it was changed to the later translation of "Mystery Man" in Pokémon HeartGold and SoulSilver. Ardos has this Trainer class in Pokémon XD during his battle with Zook, before his affiliation with Cipher is known. For his battles with the player, however, his true class of Cipher Admin is used.
Under this class, Ardos only reveals one member of his powerful team, his Alakazam. Eusine keeps a varied team, two thirds of which have some connection to mystical powers. He seeks out the legendary Pokémon, Suicune.
Pokémon HeartGold and SoulSilver
Pokémon XD: Gale of Darkness
| Trainer name
| Mystery Man Ardos
|| Initial battle
In the anime
Eusine first appeared in the anime in For Ho-Oh the Bells Toll!, searching for the Pokémon Suicune. He appeared again in The Legend of Thunder!, although the dub incorrectly referred to him as "Eugene" in this special.
In other languages
|| Mec Mystère (Eusine)|
Homme Myst (Ardos)
|| Mystiker (Eusine)|
|| Fantallen. (Eusine)|
Sig. Mistero (Ardos)
|| 수수께끼 청년 Susukkekki Cheongnyeon (Eusine)
|| Místico (Eusine)|