On the wish spell, one of the options apart from casting any spell of 8th level or lower is to give 10 creatures resistance to a certain damage type. It does not specify that it is permanent. So does this mean that you could manage to get resistance to all damage types just by choosing this option and rolling over a 33 on the d100? 

It looks like you are correct, reading it as RAW. The very next line gives an 8 hour limit on a different trait, so the fact that line 1 has no limit listed and line 2 says 8 hours, implies permanence (or rather, lack of a duration, which is the same thing). 

If this came up in my game I would have to rule that the resistance is, indeed, permanent, and if someone was able to cast it multiple times without "burning out" their Wish spell I would have to rule that the resistances all apply.

(This is just one of the reasons I do not allow Wish to be cast as a spell in my game - but only from special items like Rings of Wishing, or grants of Wishes from the gods, which allows me to control it.)

Quote from BioWizard >>

It looks like you are correct, reading it as RAW. The very next line gives an 8 hour limit on a different trait, so the fact that line 1 has no limit listed and line 2 says 8 hours, implies permanence (or rather, lack of a duration, which is the same thing). 

If this came up in my game I would have to rule that the resistance is, indeed, permanent, and if someone was able to cast it multiple times without "burning out" their Wish spell I would have to rule that the resistances all apply.

(This is just one of the reasons I do not allow Wish to be cast as a spell in my game - but only from special items like Rings of Wishing, or grants of Wishes from the gods, which allows me to control it.)

Its level 17.  I get it, wish is powerful but if thats what the PC wants to do then its gravy to me.  I let wishes be used like this BECAUSE its so rare that when it comes up, I don’t want the player to feel hamstrung.  I think that’s what it boils down to in most instances, if DMs are running wishes as they should be run, aka the rarest thing you could possibly come across?  It’s fine.

To answer the OP, they’re permanent.  Spells do what they say they do, no more or less(the last clause of Wish here is a special exception BUT its DM discretion), and since no time limit is placed on the resistance, its permanent.  The primary thing for a DM to remember here is each damage type would be its own wish.  Bludgeoning, Piercing, Slashing, Fire, Cold, Poison, Psychic, etc.  If the party is about to go up against say an Ancient Red Dragon, then maybe that wish is used to give everyone fire resistance.  That’s part of the planning of the final fight.

As a DM, I might give the dragon a mythic trait that he has a sort of concentrated flame breath that overcomes that resistance, but for the first half of the fight I’d totally let my players have that edge.  They got to level 17, they earned it.  

The chance of applying all the resistances before rolling poor to end up unable to cast it ever again by any means is really low. 

Personally, I'm OK with it. I mean as a DM I can literally make any enemy or hazard I want. They could be immune to all damage but it won't help them solve the puzzle in time before some super arcane cannon destroys the town. All the resistance in the world won't undo a creeping curse spreading over the land. Their resistance won't help against the Pryomage with Element Adept: Fire feat. 

I'll never understand why people are so afraid of wish. It's a story-in-a-box gift to the DM. 

And for those who do fear it: why not limit to the Basic Use rather than outright ban it? Seems a bit of an overreaction.

Its level 17.  I get it, wish is powerful but if thats what the PC wants to do then its gravy to me.  I let wishes be used like this BECAUSE its so rare that when it comes up, I don’t want the player to feel hamstrung.  I think that’s what it boils down to in most instances, if DMs are running wishes as they should be run, aka the rarest thing you could possibly come across?  It’s fine.

I'm not following your logic here. Do you just mean it's so rare to be level 17? Bio is saying that they don't allow Wish to be cast that way precisely because once you're high enough to cast it, it's not rare at all. There may be some physical penalties for it, but you can cast it every day if you want.

Quote from scatterbraind >>

Its level 17.  I get it, wish is powerful but if thats what the PC wants to do then its gravy to me.  I let wishes be used like this BECAUSE its so rare that when it comes up, I don’t want the player to feel hamstrung.  I think that’s what it boils down to in most instances, if DMs are running wishes as they should be run, aka the rarest thing you could possibly come across?  It’s fine.

I'm not following your logic here. Do you just mean it's so rare to be level 17? Bio is saying that they don't allow Wish to be cast that way precisely because once you're high enough to cast it, it's not rare at all. There may be some physical penalties for it, but you can cast it every day if you want.

 Statistically, you get 3 uses of wish outside the "standard" usage before you hit the "you're done" moment, and then you lose it...not just for "non-standard" wishes, but for all wishes.  The flexibility and Utility of Wish for your spellcasting is the main reason to have it...if you are using it all the time for "non-standard" wishes, you are doing it wrong (and likely aren't doing it for very long)

First of all... yes, in the majority of campaigns, it is VERY Rare indeed to have a player character reach level 17.  Personally, I have never had a 5e campaign make it that far.  Granted, we always start at Level 1, but either we have had full wipes or we accomplished the campaign without a follow up campaign or people moved or what have you, but anything above Level 12 or so is pretty rarified ground.

As for the Wish... you certainly cannot cast it every day.  There are some pretty stiff Strength penalties from the stress of casting it.  I mean, I guess you could say they could cast it again the very next day, but I would compound the stress and it wouldn't be pretty.  Not to mention rolling to forever lose the ability to cast the spell.  There are definitely drawbacks if you aren't duplicating a spell.  But I could see a party taking a chance every time there was a downtime to cast another resistance... or, you know, that 25K Diamond to pad the coffers (make sure you specify that this diamond is no larger than 2' x 4' or it won't fit in a bag of holding if that is what you're carrying).  And just hoping they didn't roll low on the chance chart.  But if it were my wizard, I would make sure that most uses were kept strictly to duplicating spell effects and finding magic wish items to try other things with if that was very important to the group.  Inherently this spell has some ways to manipulate the world, but it has some pretty stiff costs too... so, in general, I feel that it is balanced enough, just make sure you enact the penalties.  And even for a Wizard, half a tenday at 3 strength is very problematic.  

I think the next question would be, if someone was to gain a permanent resistance this way -- Could it be dispelled (either permanently or otherwise)?

Wish is instantaneous, so traditional dispel magic wouldn’t work...another wish would probably do it though

I was thinking more of like an Antimagic thing, like a beholders eye. 

The magic only lasts for an instant...there is no magic left to be affected by antimagic either