[RPG] How to practically handle the 33% chance to be unable to cast Wish ever again

dnd-5espellswish

The description of the wish spell states:

Finally, there is a 33 percent chance that you are unable to cast wish ever again if you suffer this stress.

I'm trying to figure out how to handle this limitation. The rest of the question assumes that the caster is casting wish for purposes other than casting a level 1-8 spell.

My grasp of statistics is OK. My DM's? Less so.

How I expect it works: every time I cast wish there is 33% chance I may never cast it again. But I want to cover the naïve questions I expect that my DM is going to have. For instance:

  1. I want to know if a caster is bound to not be able to cast wish anymore, meaning that in the best case after 33 casts without suffering the stress, the caster will definitely suffer it on the 34th cast.

  2. I would like to know who or what decides that 33 percent is achieved. Does a die have to be rolled? Must another random mechanism be used? And who triggers it: the DM or the player?

  3. If the DM/player wants to roll, can the roll be a d6, or must it be a d100? The spell says "33.0" percent, right? Not 1/3 (or 33.333… percent). So a d6 can't be used, can it?

  4. Can feats, abilities or spells altering the roll be used?

Best Answer

I first want to know if a caster is bound to not be able to cast wish anymore, meaning that in the best case after 33 casts without suffering the stress, the caster will definitely suffer it on the 34th cast.

If the caster fails their "stress test" then yes, they are bound do not be able to cast wish anymore. But the "33 tries, then fail on the 34th" isn't how probability works. (This is; the short of it is that "best" case is that the stress test never fails, but that 70% of casters will experience that failure by their third casting.)

Second, I would like to know who or what decides that 33 percent is achieved. Does a dice have to be rolled? Must another random mechanism be used? And who triggers it: the DM or the player?

You are free to execute the mechanics of D&D however you like. Most people use dice as their random number generators. Many use high-quality computerized PRNGs that feature animations of dice in their readout. You can flip coins, draw cards, pebbles from an urn..., or anything that your group agrees upon. For standardization the authors assume everyone is using dice and they use dice notation to express quantities.

The player triggers it, by casting wish. Whether the player or the GM rolls (or otherwise initiates random number generation) is up to your table's conventions.

Finally, if the DM/player wants to roll, can the roll be a d6, or must it be a d100? The spell says "33.0" percent, right? Not 1/3 (or 33.333... percent). So a d6 can't be used, can't it?

The spell indeed says 33%, so you're right that "1-2 on a d6" isn't quite RAW. It's off by 1-in-300. Your table will have to decide whether that level of error is tolerable if someone wants to use a d6 (or d12, even!) in place of percentile dice.

Also, can feats, abilities or spells altering the roll be used?

It's going to depend on the feat/ability/spell. But it's almost certainly "no," given the wording of many of those abilities. Note that this roll isn't an attack, check, or save, which Halfling Luck or [dis]advantage would require. The Lucky feat or divination wizard's Portent require a d20 roll. Bless or bane or guidance... none of those would apply. The point being: the source of a die modification should tell you enough as to whether it'd apply to this roll.

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