Complex sentence: One of the party members is a non-playable character (NPC) and belongs to the main character's world, while the other two party members are NPCs borrowed from other players by connecting online or are locally generated by the game.
Split into simpler sentences: One of the party members is a non-playable character (NPC) and belongs to the main character's world. The other two party members are NPCs, which can be NPCs borrowed from other players by connecting online or locally generated by the game.