Tony Vargas said:
Only if the player is adverse to said chaos (there's always the 'joker demographic'). Which fits, the idea is that magic is dangerous, unpredictable, unnatural - just witnessing it can drive you crazy, afterall.
I get the impression that PT doesn't cater well to the mischief-makers, what with the dark tones and the madness putting a particular kaibosh on "whimsy." I don't think my Lewis Carroll-inspired gnome would go down well there, even if he was a rogue instead of a sorcerer.
But for my stance, suffice it to say that there's significant cause to doubt the received wisdom that "casters rule in D&D" when it comes to the most recent edition. That doesn't mean one shouldn't play a low-magic party in 5e, but that DOES mean that if your reason for doing that is because "casters dominate the play experience" (or something to similar effect), you might not really get the dramatic difference you're looking for by doing that. It might be like taking off your shoes at an airport or taking homeopathic remedies - a pointless solution for a problem that looks worse than it really is and that also doesn't actually do much to functionally improve your game, but maybe makes you
feel better. Not that that's inherently a problem (we all do our thing), just that it might not wind up actually achieving the goal you're looking to achieve.
For PT specifically, it doesn't sound like the setting really wants to gimp casters, per se. Playing a caster in PT might be like playing a warlock in regular ol' D&D - you're a dark character who trucks with dark forces. That doesn't mean you have to be punished for the choice. It's not like Fiend warlocks have to roll on a random chart or be evil for a while, anymore than fighter characters have to roll on a chart to see if they're affected by PTSD from all the orcs they murder or whatever. Totally fair to add those elements, but it's also probably worth examining why the designers didn't do it, and specifically asking the question, "What if they
meant to do it this way? Why would they make that choice? How do they
expect the game to be used by your hypothetical Average Table?" If only because then you can more accurately judge the costs for going against their design decisions at your own table.
My point here isn't to say "don't force low-magic parties" it's to say, "be honest about WHY you're forcing low-magic parties, and try to look objectively about if your goal is actually served by that action."
Meanwhile, if you just want to add some fluff to make spellcasting more meaningful in PT's context, consider a chart of minor cosmetic effects, like "when you cast an enchantment, everyone hears the voices of their dead loved ones pleading for release for a moment...and the victim hears these voices the entire time they're under the influence of the spell." Or "While maintaining concentration on a spell, you babble in tongues and wormlike creatures are seen moving under your skin." Appropriately ookey, and definitely cause for the locals to sharpen their pitchforks, but not "SCREW YOU, MAGIC-USER!"