Complex sentence: Typically, they are aggressive non-player Pokémon trainers, challenging the protagonist upon sight, although several important characters, including Bill and Mr. Pokémon, are called Pokémaniacs.
Split into simpler sentences: Typically, they are aggressive non-player Pokémon trainers, challenging the protagonist upon sight. However, several important characters, including Bill and Mr. Pokémon, are also called Pokémaniacs.