Experience, Not the XP Kind…
What will a person experience if they play this game? I think that is a question that all GMs should ask themselves before planning a session, adventure, or campaign for an RPG. It helps a GM to focus on a desired effect for the game. Thinking about how you want the players to feel during the game gives you a goal to work towards.
Do not just brush this question off with the standard gamer response of "To have fun." Not only is it too vague of a goal, but it is far too limiting as well. That paradox exists because what one person considers to be fun may not be fun for another person, and so a GM might then go for the lowest common denominator in order to run a "fun" game.
For example, you have one player who finds roleplaying to be great fun and another who finds tactical combat to be great fun, but both find puzzles to be somewhat fun. Your goal is to run a fun game, so you end up putting in just enough roleplaying to satisfy the one player, and just enough tactical combat to satisfy the other, and then a whole lot of puzzles as filler. The result is that none of your players will have a game that is intensely fun, but instead will have a little bit of fun with the occasional intensely fun moment.
What if you had chosen to try and induce fear in the players instead? Or what if you were even more precise and chose to induce fear in the players of one particular monster? Now you can design roleplaying scenes where the NPCs are terrified, and they convey that sense of horror to the PCs. When the monster battles the PCs it can be a frightening opponent with its extreme tactical prowess. Any puzzle that you do include in the game should reveal something scary, or should have terrible consequences for failure to solve it. Both of your players are now experiencing the desired effect that you had planned for not only through their preferred feature of the game but through the game as a whole.
Try it when planning your next game. The odd thing is that if you can pull this off your players will probably have great fun even though that was not your specific goal.