Well, over the long haul player knowledge will only work part of the time, too. Right?
Basically your thesis that player knowledge trivializes combat could only be true if knowledge skills were generally acknowledged to be so powerful as to be OP. But nobody claims that.
You seem to be claiming that occasional player knowledge (which may or may not be accurate) trivialize combat, but rolling dice for that same knowledge (which may or may not succeed) does not.
The players in your example did not describe what they were doing other than the order in which they were marching. Without additional information, the DM has to assume and establish what the characters are doing while traveling, which (1) is not the DM's role and (2) makes it harder or impossible to adjudicate. So ideally the players each say what they are doing while traveling in their marching order.
If they all say they are staying alert to danger, then the DM has to decide who in the marching order has a chance at noticing it based on the danger's positions relative to the party. For those characters, the DM may call for an ability check if the outcome is uncertain and there's a meaningful consequence for failure. If they are staying alert to danger repeatedly over time, then it may be a passive check.
Only if the DM changes things up a significant portion of the time. Otherwise it's pretty much always going to work.
I disagree with that assessment. Knowledge skills only have to be at the baseline for the game, not over powered for what I'm saying. However, if you use player knowledge not only to you completely invalidate monster abilities, but you also completely invalidate the knowledge skills in many situations, and regarding creatures pretty much completely. That's what is OP.
Occasional player knowledge?! It's occasional in the same way as there are occasionally weeks where I don't have to work.
In the example in the DMG, the character was not paying attention and still got a check. I guess I don't usually find it worth making the players remember specifying that they're taking their usual precautions.
Thinking back to a previous question I had... Giving a character who says they're watching the crowd going down the road a pre-emptive knowledge check to identify the family of a knight who stands out, seems similar (assuming their passive check would have noticed the knights existence). Or is perception fundamentally different in RAW?
Either knowing monster abilities trivializes the encounters, or it does not. If it does, then a simple success at a knowledge skill (maybe one roll for each person in the party, plus guidance) will trivialize the encounter, and having high modifiers to those skills becomes vitally important.
That just does not happen.
Why would a DM want to prevent a player from using simple machines?There are a large number of things that are harder to wave away than gun powder. It feels strange to have to declare some combinations of arithmetic and the simple machines don't work just to thwart an entrepreneurial character (anything involving more than five simple machines in tandem are attacked by gremlins?). Taking it out-of-the-game and dealing with it as real people seems like the obvious solution to me.
The baseline assumption, stated in the rules, is that characters are usually alert for danger. I'm not going to require my players to add, "oh, and I look out for danger" to any action declarations they make, they get that as assumed -- if it's compatible with the action declared, at least. This last is a pure GM judgement call, which isn't surprising in that 5e's unspoken core mechanic is "GM decides." I'd recommend making sure a player understands that a given action would preclude being alert to danger, but that's advice, not rules.In the example in the DMG, the character was not paying attention and still got a check. I guess I don't usually find it worth making the players remember specifying that they're taking their usual precautions.
This isn't resolvable with the information provided -- something's missing. Why is the player watching the crowd, for instance? A good action declaration requires both a method -- the how -- and a goal -- the why or what. You've given a method, but not a goal, so I don't know if calling for a check (or refering to a passive score) is appropriate in this situation. If it's a roll to add flavor, that's not how the system is presented, but it's a fine way to use it to determine if something interesting is present. Not my style, though, but I can see it.Thinking back to a previous question I had... Giving a character who says they're watching the crowd going down the road a pre-emptive knowledge check to identify the family of a knight who stands out, seems similar (assuming their passive check would have noticed the knights existence). Or is perception fundamentally different in RAW?
Why would a DM want to prevent a player from using simple machines?
The idea that weaknesses, resistances, immunities, and special abilities like a troll’s regeneration “might as well not exist” if the players know how to exploit or circumvent them (and are allowed to do so) is absurd. Those abilities still force the players to use particular tactics they would not otherwise have to use, thereby increasing the challenge of the encounter.Depends on the adventure, but I like to switch up monsters and not repeat a lot just as a matter of personal preference. If they're in the troll moors, they'll encounter trolls whether they know about the way around the regeneration or not.
That doesn't change that if there's never a point where the regeneration matters, it might as well not exist.