Are there any drawbacks to using a wish spell to increase ability scores? If not then what would stop players from just using wish repeatedly and raising their ability scores to 30?
I'm just getting back into RPGs with D&D 5e after not playing for years, and I seem to remember this being covered in the editions we played back then.
The stress of casting this spell to produce any effect other than duplicating another spell weakens you. After enduring that stress, each time you cast a spell until you finish a long rest, you take 1d10 necrotic damage per level of that spell. This damage cannot be reduced or prevented in any way. In addition, your strength drops to 3, if it isn't 3 or lower already, for 2d4 days. For each of those days that you spend resting and doing nothing more than light activity, your remaining recovery time decreases by 2 days. Finally, there is a 33 percent chance that you are unable to cast wish ever again if you suffer this stress.
A part that could be up for debate by some; is the 33 percent chance to be unable to cast wish again only if you cast another spell before recovering from wish, or does it only apply at a time you cast a wish that does not duplicate another spell.
The mention of stress in the last part of the quote ties it back into the first part where you suffer stress for casting wish that does not replicate a spell, and therefor each part applies, to such a casting.
When casting wish that does not replicate a spell,
This is one of those spells that DM's need to be very careful what they do and don't allow. But basically every time they try cast wish in this manner they run the risk of never being able to cast wish again.
I think the most relevant reason to be careful here is in the paragraph right after the list of alternate things you can do with Wish. Emphasis mine:
You might be able to achieve something beyond the scope of the above examples. State your with to the DM as precisely as possible. The DM has great latitude in ruling what occurs in such an instance; the greater the wish, the greater the likelihood that something goes wrong. This spell might simply fail, the efeect you desire might only be partly achieved, or you might suffer some unforeseen consequence as a result of how you worded the wish.
"So you wanted your intelligence to be 30, right? Great! Hmm... seeing as this list here doesn't include permanently increasing ability scores, I've decided to grant it with an 'unforeseen consequence'. You're now a sentient tome of magic. Since your new body doesn't have appendages at all, you can't cast spells with verbal or somatic components. Oh, lacking eyes and such will make it awfully hard to read your spell book and change your prepared spells...
"What's that? You want to amend it so you keep your own body? I am a generous and forgiving DM, so I suppose I'll allow that. Unfortunately, the spell has to cannibalize your own body to make (and make room for) that bigger brain of yours. Your skull is now much thinner, so you take an extra d6 of damage whenever you take damage. You can't move too quickly, either, for fear of smashing your oversized brain on that cramped skull. Oh, and we had to borrow some of those nerves from your hands, tongue, and muscles to make more brain matter. Your dexterity goes down 5 points, and you no longer have the fine dexterity needed for those verbal/somatic components..."
Overall, the game has some pretty hard caps on ability scores with the intent of keeping the balance with respect to high-level monsters. You literally risk everything your character (or the party, or the world) is/has to bend those rules.
Suffice to say that simply being unable to cast Wish ever again could well be the best thing to happen to you all day.
In 5th edition Wish is not stated to be able to grant ability score increases as any of its specified functions. In order to possibly gain such an effect you would risk either the spell failing or an unintentional consequence of the Wish occurring. Even if the spell is cast with no ill effects the caster still suffers "Wish stress" and every instance in which a spell caster suffers such stress there's a 33% chance that the spell caster will lose the ability to cast Wish again. The odds aren't in their favor after the second casting. A spell caster capable of casting Wish is better off searching for tomes than attempting to increase one ability score to 30 for one PC.
Wish is a calculated risk every time that it's used for anything other than its most basic function so while it is theoretically possible for a PC to use the spell to increase all ability scores of every member of a party to 30, it's extremely likely that they will fall very short of their goal.
Basically? Wish is a spell that can do more or less anything. Want to get rich? Wish! Sex change? Wish! Want to gain 20 levels of fighter? Wish! It is overpowered as a spell can get. Hell, you could use your 1st wish to stop yourself from suffering the negative effects of wishes, if you word it right. It is the be-all, end-all holy grail of spells that every wizard levels 1–16 dreams about. As long as you are clever in your wording you can do anything.
Just a note, the wish spell does indicate that whatever you ask will be done in the easiest way possible. Money is not created ex nihilo, gender or race changes can delete class levels, and your permanent haste spell may take forever to wear off. I am in no way responsible for the ill effects of a wish made in good or bad faith.
