All true, but those are PCs influencing NPCs. We're looking for examples of the less-common reverse, where NPCs can influence PCs without magic.
You want one from outside D&D, perhaps?
Let's look at FATE. Generally, in Fate-based games, social or mental conflicts are on the same mechanical basis as physical combat/conflict.
As you take hits in conflict, you take stress. If you run out of available stress boxes, you get "taken out".
You can shunt some stress into Consequences. The player gets significant say in what the consequences are, but needs GM approval (largely to make sure they are appropriate severity). But, you can only take so many Consequences.
To end the conflict, there are two choices:
First, someone may concede. If the player (not the character, the player) concedes, they get to narrate the conditions of their loss, so long as they don't negate the fact that they lost. So, for example, if it is a fight, the player can concede, and narrate how they get beaten, but escape out a window. The side that concedes can also end up with some Fate points to use later.
If nobody concedes, then someone will get Taken Out. This is like conceding, except the *other guy* gets to narrate how you lose, within the scope of the conflict and social contract of the table. If you are in a knife fight, and it isn't a "no PC-death" game, then if you get Taken Out, the other guy can say, "...and I kill the character."
So, if it is within the social contract of the table, you can imagine a party scoundrel-type getting into a social conflict with an attractive person at the inn - "Who seduces who?" This could easily end with the narration that the PC is seduced, and in the morning they find that the key to the ancient treasure vault has been stolen from their pack. No magic involved, but within the scope of the conflict, the PCs actions can be narrated by someone else, all within the rules.
The bottom line in this system is that if you don't want someone else narrating what happens to you, you do not fight to the last stress box. If you soldier on, you are accepting any result within the scope of the conflict.