DM: Everybody roll a Perception check.
Yona (FS): <roll> Oh! Natural 20.
Ocellus (TS): I don't think any of us are going to top that.
Gallus (RD): I'll have you know, <roll> I'm purpose-built for… Nevermind.
DM: You all hear a clanging and shuffling of hooves. But Yona is the first one to peer through the bookcases and see into the back of the library. In the very back aisles, there is a large ornate metal grate, presumed to be just a drain. But it's clearly been opened moments ago, and Cozy Glow is coming out of it with a lantern. <roll> She doesn't spot you as she smugly hovers out of the library.
Silverstream (PP): We were in here for a while, right? How did she get over there? What's down there?
Gallus (RD): Let's go ask her.
(beat)
Gallus (RD): Oh good grief – obviously I mean "tail her, spy on her, interrogate her, and fight her, not necessarily in that order."
Ocellus (TS): Phew, I was getting a little worried…
Um, yes? They are? They’re not necessarily an auto success; for example if you roll a nat 20 on perception but have a negative Wisdom modifier, you could still end up failing the check if the enemy rolls high enough. But there is absolutely nothing preventing you from rolling a Nat 20
Of course you can roll a Nat 20, technically, as long as you only mean "rolling 20 on the die", which is kinda obvious because it's not like the die loses a face.
In practice, "Nat 20" on an ability check is "I rolled 20 and now add my modifiers", which means you are (usually) still expected to communicate your final result. I think that's what Anon might have been hinting at by pointing it out.
Actually, it's common practice to call for rolls when your players ask to do something ridiculous with a natural 20 representing a mitigated success, especially if you don't want to give away that something is impossible.
That works with any game, really. I was in a Mekton game a long time ago, for instance. We were attempting to stop an alien race from stealing the lost human super-battleship (this is mekton, after all.)
They were in a combat dropship, and had a substantial lead on us, and would almost certainly reach the command area first. We were all in mecha with booster rockets attached to our backs. Lacking any other means of stopping them, I told the GM that I would uncouple the rocket and use it as a dumbfire missile to knock the alien ship off course, and buy us a better chance against them.
The GM just sort of gave me this *look* and said there was no point calculating how impossible this was. I needed a critical success to do this, and no matter what happened, I would get to the fight last, having decoupled my booster rocket.
I agreed, and rolled percentiles. I rolled a critical hit on a random roll. The GM just snickered, and said that the bad guys get their dropship hit by this giant booster rocket that flew drunkenly across the battlefield to hit their dropship and knock them off course. They still got to the ship first, and we still had a fight on our hands. But it wasn't a mad rush to the command deck.
A good GM will roll with stuff like that, especially when the dice roll in the players' favour.
I agree.
Storyteller (nwod) has this as a "chance roll". No matter what the odds, you can always go for a 10% chance of minimal success. If you use the (optional) botch rules, you also have a 10% chance for a critical failure, though.
Yes of course you can still roll at 20 on the dice, but exclaiming "Oh! Natural 20!" isn't helpful since it doesn't do anything special in 5e, you're only after the total. This lap in rules knowledge is continued by Twilight saying no one else would beat that, when that's absolutely possible. Barbarians typically don't focus on Wisdow, so say Fluttershy got a 20+1=21. Anyone with a wis mod of 3 can still beat her by rolling 19.
"Natural 20s" don't do anything special on ability checks in 5e.
I don't think they did on skill checks or ability checks in earlier editions either. It's just attack rolls and saves where natural 1s and 20s mattered, since there are no certainties in combat. (But there certainly is "you are not strong enough", "this is beyond your ability", and so on with skill and ability checks.)
Twilight doesn't say no one else CAN beat Yona, only that she doesn't think anyone WILL. The phrasing indicates that Twi does recognize that a nat 20 isn't auto-success in 5e, since there is no such thing as beating an auto-success.
True, but if Flutter just said "I got a 24" it could've just meant she was also purpose-built to detect, so it may have needed additional clarification to make Dash' response meaningful. I think the "oh! Naural 20" was in service to the joke, more than her believing she got a crit success. That is supported by the fact that Dash thought she could beat her by numbers alone (which isn't possible if crit successes are a thing).
I think I recall seeing them as a rule variant in the PHB. Or maybe the DMG. And there's always house rules, too. I know my 5e group seems to have critical successes, though not crit fails.
Considering that Dash's player proceeded to act as though she had a chance to beat it, that means it wasn't an auto success, just a very high roll.
Since 5e doesn't have skill points, its not hard to assume that any player who doesn't have an outstanding wisdom or other bonus isn't going to beat another player who got a 20, since most of the bonus is proficiency, which we can assume a barbarian would have since they don't have many great options.
Assuming the DM knows she's proficient, saying the roll is helpful enough to know that it passes the DC, while Dash's player might still be able to beat it should she have a better bonus.
The real issue here is that this should have been passive perception, not a roll.
"This is it, my moment of glory, where I show all I'm good for, my ridiculously specific specialty, I drop all I have into this one att-aaand it's a fumble".
Solitary Performance, I got a deal for you.
*hands a blank piece of paper and a pen*
All you have to do is sign the paper, and you'll get your fantasy prize for winning the contest.
That's right, you won.
One signature for one prize.