Chaos doesn't tempt good people by just offering them what they want. It tempts them by offering what they cannot refuse to accept.
[...]
I think people saying that only a fool would accept Chaos are kinda overestimating the level of choice characters have. Yes, someone like Mathilde can Just Say No to Dhar, but for others it isn't as simple.
Extremely good argument. In the RPG, you basically have to claw out every single advantage you can to cast something. There, you can't really 'reliably' cast something, and the amount of dice you have to cast at all are pretty limited. There's your raw power as a wizard, but there's also circumstantial bonuses like how variable the Winds are, any ingredients you may have, and that's just getting into the common stuff. For rarer stuff, there's Power Stones, but those are called out as needing weeks or months to make. And there's also the familiar bond possibly granting a +1 to Magic.
And finally, we have the forbidden method. A player may feel the need to get a +1 to Magic from boosting a spell with Dhar via the Dark Magic talent, even though that explicitly means it's more likely to miscast, and turns regular miscasts into more dangerous ones.
It's not hard at all for me to imagine a desperate player feeling the need to use that temptation. What if you're in a really desperate situation and you've had a string of bad rolls while casting, where you didn't have enough juice? And well, maybe you'll just use it here and there, it's not like you're going to be embracing Chaos anytime soon. You just need a bit more power to your spells, is that so much to ask? And nobody needs to know. Nobody but you, and perhaps your companions, if they know enough of magic to even realize...
Mathilde certainly went through the trial of temptation of using Dhar back in Sylvania, and before she had the chance to worry about it again, she was lucky enough to get the +1 to Magic from Wolf, and also, cashed in her Drakenhof deeds from Kragg. Most people do not get so lucky as with the former, or have that opportunity with the latter.