Consider this exchange between a player and a referee: Player: “Can you add [5e race] into [System]? I really want to play one.” Referee: “No, I bought [System] for a reason and don’t want to deviate too much.” P: “Then why are we using the sailing system from [different System] instead of these ones. Gunpowder isn’t in [System] either.” R: “Those are different because they are part of setting the campaign tone”