Intimidating Charisma
A question was raised recently about why charisma was the ability linked to the intimidate skill. Surely, the point was made, if something has low charisma and is thus ugly and unbearable the easier it is to intimidate someone. Well, perhaps, but that is missing the point of both charisma and the intimidate skill. Intimidating someone can be much more than making them quake in fear at your frightful presence, opening up their guard, although given that most of our games are based around fighting encounters it is understandable why this use of the intimidate skill is the most prevalent in the mind. But intimidation could be making you go on a dangerous quest, taking a bad deal on some goods, or some other form of bullying, generally because the alternatives given to you don't bear thinking about. It's making someone do something they don't want to, and, unlike using diplomacy or bluffing, it is often achieved using threats.
This is partly why a big and scary monster won't necessarily have a good skill modifier for intimidate, because it doesn't have the wits to manipulate someone in such a way as intimidating demands. Now, if you or I were to meet a zombie, or worse, in real life we would probably be rather scared, but this wouldn't be through intimidation; it would be a simple, primal fear driving us. RPG heroes, such as most player characters are, kill zombies before breakfast, as a quick workout, so aren't scared by these simple monsters, and they encounter much worse throughout their lives, rarely taken aback by the horrors they witness. They are heroes, after all. However, if a monster has particularly horrific features, enough to scare even a hero, then there must be a game mechanic to have this occur. This isn't done with the intimidate skill, though, but will likely be achieved with a special quality of the creature, like a fearful presence. You will note that this will be a simple, primal fear, and won't be based on charisma.
It should be clearer why there is a difference between a fearful presence and being intimidated by a creature of some sort, as being scared and being bullied are different in cause and effect. Now we can examine why the intimidate skill is based on charisma. If you tried to make someone do something for you, perhaps something they would rather not do, you have some options available to use. As noted above, you can try to be diplomatic, be that person's chum and use persuasive skills and bartering to achieve the desired result, or you can bluff your way through and make the task seem less arduous or dangerous than it sounds, or you can try to intimidate them, getting them to do what you want by force of will alone, perhaps with threats, veiled or otherwise. Note that all of these options use in-game skills that are based on charisma. Charisma is a measure of personality, of belief in yourself and how well you can project that belief on to others.
It doesn't matter if you are particularly good looking, or rather unattractive, as that isn't what charisma measures, even if looks can help with one's initial impression. After that initial impression, though, your looks will play a much smaller part. I am sure we can all think of someone who is physically attractive but who you wouldn't believe a word they say, nor feel threatened were they to attempt to intimidate you, simply because they don't have the force of personality behind their words. An easy and perhaps universal example to use would be school teachers: there is generally at least one teacher you can remember who had little control over the classroom, and another whose pupils wouldn't have dared breathe without permission. Those teachers' appearances played little part in how they controlled a class, but their general presence was clear to anyone. And that is charisma.
The intimidate skill is based on charisma because it measures how well you can force your will on others, and precisely because neither the intimidate skill nor charisma directly relate to someone's appearance. It is the power of belief in yourself, and with that belief you can achieve more than a lack of confidence could. From this it can be seen why turning undead is based on charisma, as are a sorceror's spell-casting abilities and using a magical device. Charisma is a strong belief in something, normally yourself and your abilities, coupled with the confidence to get away with whatever you're doing.
The only thing I am left wondering is why Will saves are based on wisdom and not charisma.