I like it, there is also some other monster descriptions that hint at abilities those monsters should perhaps have, that I think should also be looked into. So, obviously yes to this from me.

I never noticed that in the monster memory. I like the proposal, but the special damage shouldn't be too high. -Acid is the rarest elemental resistance in the game, and these guys are already frustrating enough when they rust and destroy your stuff.

Oh yes they are frustrating but they are also quite manageable by simply throwing (quite abundant) iron stuff at them, or wearing artifact weapon + artifact gloves.
They typically touch those items much more often than other types. Sometimes it's safe to remove corroding helm/boots/girdle but the trick with gloves works most of the time.
Additionally, acid resistance is very easy to obtain, almost guaranteed with that anthill in PC:2.
Sometimes corpses might not appear after killing the ants, but usually at least one will be available.
Also there are giant slugs that grant a guaranteed acid immunity when eaten blessed.
Personally, I think that acid is the most abundant and easiest to obtain intrinsically of all the resistances/immunities in the game.

None of the monsters that deal acid damage do so on-hit, and the monster description doesn't outright state that the acid is harmful to creatures; it's corrosive for iron weapons and armor. Compare that to stuff like gray oozes, which can damage adamantium, and even they don't deal acid damage to players; only if they strike at them with their bare fists. It wouldn't make sense if rust monster acid, which can only affect iron, would end up doing more damage to PCs than "elemental" acid.

Rust monsters already cause rust, and I don't think they were intended to do anything else. Don't take the monster memory too literally - it was created a good while after the creatures were designed, and I think Thomas didn't write all of it.

Every now and then I'll give one the elemental gauntlets or another iron artifact, just for kicks. The reaction is always funny :)

The anthill in the PC will do most of the time, but you might not get a corpse from it, and if you're very unlucky you'll get one but it won't grant the intrinsic. And not for nothing it's a little Christmas every time you land a giant slug corpse. They're hard to obtain unless you have ammo of hunting. So in comparison with the other three elements, all of which have at least one guaranteed source of resistance, -Acid is the rarest.

Personally I'd say poison is the most common intrinsic resistance to obtain. Spiders, spiders everywhere. And all those fire lizards and fire beetles running around make fire resistance pretty easy to get, too.

In the past ~5 games that I remember, I always had acid resistance early on. I don't know but maybe I'm just lucky on it.

I object to this for the same reason as Silfir.

So? Don't tell me they don't, tell me why they shouldn't.

It also doesn't state outright that their *claws* are harmful to creatures; they're meant for scratching at rock seams in the dungeons. I inferred these things from a general understanding of the nature of claws (and acid) -- and in the latter case by deducing that any acid that can destroy iron in seconds is obviously incredibly corrosive, and observing that incredibly corrosive things are harmful to creatures.

You make a good point. Grey oozes obviously burn on contact with bare skin, so they should likewise burn when they strike (IF they are able to make flesh-to-flesh contact, such as if the PC isn't wearing armor). Perhaps another RFE is in order.

What wouldn't make sense is for their acid to only affect iron. And nobody said anything about causing a lot of damage. I was thinking a few points per hit (no more than 1d6 at most).

I'm pretty sure you're right about him not writing all of it, but it also happens to be the only thing we have to go off to get a more detailed feel not just for their stats and abilities and the raw numbers, but what the creatures in the game are actually supposed to be like.

We have another thing - what the monsters actually are like. ADOM wasn't just created last year; gray oozes and rust monsters have been the way they were for several versions before 1.1.1, well over a decade. Thomas didn't roll his head over the keyboard and voilà, gray oozes, he designed them the way they are right now. It's not that his design choices are sacred and disagreeing with them is blasphemous; it's that I think both gray oozes and rust monsters are perfectly fine right now and 1.2.0 wasn't put in place to fix stuff that wasn't broken. Keep in mind; you now want to change not just rust monsters, but also gray oozes and ochre jellies, based on your particular interpretation of a line in one monster's description, and that change entails a type of special attack that isn't even in the game. It would have to be specifically implemented. What even for? It's not that rust monsters aren't already pretty strong and plenty annoying to deal with. Gray oozes and ochre jellies already need to be played around plenty, and they multiply - acid damage on hit would turn the random creation of even one into a potential death sentence. Acid resistance, as people have pointed out, is a luck-of-the-draw thing; either you've been to PC:1 and scored an ant corpse, or you didn't get one or didn't think you'd have to. Those are balance concerns that we have no reason to even entertain, considering all this suggestion is based on is one line in one creature's monster memory.

No no, this suggestion is for rust monsters alone. If I were to post a suggestion for jellies and the like, I would do so separately with supportive rationale. And I really don't think it fair that you're trying to dismiss the suggestion as being just my "particular interpretation of a line in one monster's description." It outright says their claws drip acid. I don't see that there's much open for interpretation there.

Well, it could be that you didn't read my previous posts. It also says that the acid causes corrosion in weapons and armor - it says nothing about whether or not it does anything to creatures. Not all acid is created equal.

Didn't you just try to tell me that it's fine if we add acid damage to rust monsters despite their acid being less potent than gray oozes' because we can add that damage to gray oozes, too? Could you stick to one or the other, please?

No, I'm pretty sure I covered that point already. Perhaps you didn't read mine.

What I said is that this particular suggestion was intended for rust monsters alone. The gray ooze notion is interesting, but I'm not campaigning for that here.

I like it, but with the following caveat -- they should only cause acid damage to the PC if the PC is not wearing armor (or if they punch through the PC's armor). Else the acid would just get on (and corrode) the armor and not actually contact the PC's body.