In the Defense of Absolute Power
So, let’s talk about a topic that I feel is fairly underrepresented (at least properly) in discourse about tabletop RPGs, that is the prowess of high-level characters, specifically spellcasters. I’m specifically referring to the effects of the vaguely-defined, exceptionally powerful spells, the ones that (GMs fear) can totally derail campaigns if left unchecked.
The spells in question are like your Wish, True Polymorph (or equivalent), Permanency, Contingency etc. These are the kind of spells that a powerful spellcaster (specifically a wizard 90% of the time) uses to circumvent some of the conventional restrictions of the game in terms of the power of player characters.
I’m in favor of a liberal approach to these spell powers, particularly if the player [wizard] in question is willing to cooperate with the GM.
Now when you look at forums into how to rule these spells, you’ll quickly find a vocal majority championing the most restricted interpretation of these spells. AKA: Wish (the ultimate Arcane spell) can only be used to replicate lesser spell effects without surrendering the entire effect of the spell to your GM. Keep in mind, in some editions, Wish has a hefty material cost for a single casting. Or Polymorph any Object can only be used to replicate a lesser polymorph spell/improved baleful polymorph, albeit with a potentially permanent, superior duration.
This is clearly done in an attempt to reign in the powers of player characters at high levels. However, I’d argue that this is absolutely frivolous, as any Wizard above like 10th level has the ability to completely break a campaign if they wished, dimply due to their class’s sheer magical versatility and the power of mid-to-high level spells.
Per the rules, nothing is stopping a Wizard from doing the required research to prepare a ritual that calls a powerful outsider (like say a demon) to the material plane, bind it and kill it upon summon, then animate the corpse as some sort of powerful undead minion. You can keep it under your control by having a simulacrum maintain control while in some sort of extra-dimensional space, and pull it out whenever you need some disposable beatstick stronger than the rest of your party. Arguably that’s not even the most egregious of actions in terms of alignment, as it involves you slaying a powerful evil creature. Sure, I’d argue you couldn’t be good-aligned, but you could get away with being neutral and doing that.
Anyways, if your player wants to use powerful transmutation magic to permanently change themselves into an outsider, or half-dragon etc. You should let them with these powerful spells, essentially if you make clear a reasonable, in-universe drawback. Something along the lines of this “you use a combination of polymorph, empowered by wish spells to convert yourself into a mighty angelic being, however your soul has difficulties adjusting to your celestial form, removing all spellcasting and possibly other magical effects (even those inherent to the form) for an extended period of time as you acclimate.
Now this doesn’t mean that you lose all your class levels, but rather that you are whatever base creature you change into, with all your class levels, however you take negative levels equal to whatever level your character was that can’t be recovered by a restoration as your soul is in the process of adapting to your new form. You’d start off by giving the player the powers inherent to their new form, and after that has been completed, you can slowly give them their casting abilities back.
As for wish, you really shouldn’t take that as a sorcerer if it has a material cost that can’t be hand-waved by eschew materials, and a wizard should only prepare it when they want to warp reality. Wish should be interpreted as the ultimate expression of a mastery of the arcane arts. It’s not a parlor trick you use every day, but rather something you utilize when realizing the pinnacle of magical powers.
Also remember, you’re the GM, if a player character is problematic and refuses to improve when you talk to them about it, you can kill their character. There’s no reason to preemptively punish good players for getting into the headspace of their class and wanting to go big-brain arcane caster.
