Professor Cypress: He is both the professor and water type Gym Leader of the Ellenia Region. When doing neither of those things, he enjoys relaxing on the beaches of the thousands of islands of Ellenia. His ace is Ellenic Kingambit (a Dark/Water type). He gives the Beach badge to trainers who defeat him.

Nicholas is your rival who likes to find rare pokemon. His main goal is to defeat the main legendary pokemon of the Ellenia region (he sees you as an obstacle to be overcome). He chooses the starter strong against your starter (placeholder Blastoise). (His reuniclus and hydreigon are the Ellenic regional variants which are Poison/Dark and Water/Dragon respectively. His aegislash is just a placeholder)

Leonidas is the Fighting type gym leader. His ace is the Fighting/Steel type Sparthundred which evolves from Falinks. He gives the War Badge when defeated.

Socrates is the Psychic type gym leader. His ace is the Rock/Psychic type Jewelgantic which is a regional variant of Coalossal. He gives the Thought badge when defeated.

Constantine is the Rock type (and final) gym leader. His ace is Staturigus, a Rock/Ghost regional form of Cofagrigus and Runerigus. He gives the Legend badge when defeated.