Which hazard did you pick? Keep that in mind. Ok, when the player tells you he climbs over a wall, how do you know whether or not he encounters the hazard you picked?
He has to tell you which wall.
and again (like a broken record) in the very rare case I do have to ask (of course that requires the following to all line up... I described a detailed obstacle, the player didn't feel like giving a major description, I had pre set a trap or something, and I am not willing to hand wave past the trap that the Player showed he wasn't intrested it)
And again (like a broken record) D&D is full of hazardous situations. And the examples of the wall and the room with the assassin or trap are just examples. Do you get, finally, that I need to know where the PCs are standing to fairly adjudicate traps, and determine who might be affected, among many other things which can happen in the game?
If I present you a room, and your character stands in the doorway looking for traps, or for treasure, or for a hidden enemy you think might be in this room, there is a reasonable chance that the PC won't be able to see them from the doorway. There is a nonzero chance that they will become obvious if he moves some place in the room where he gets a clear view of the sought thing. If you refuse to tell me where in the room your character moves, I am unable to adjudicate whether a) you find the thing you're looking for without even needing a roll, b) you get another opportunity for an ability check, or c) you trip a hazard of some kind.
You can literally see in the post you quoted that I acknowledge you might have allowed the save. That doesn't actually address my point in anyway, because you wouldn't allow the check to detect the trap.
I already determined what chances there were to see the hazard (we haven't established yet in the example if it's a pit trap under the rug or an assassin totally hidden by an alcove, out of LOS) from the door. It was not successful. What does the PC do next?
Because you are saying it is "an example of a situation where a character can automatically see a previously completely hidden foe if they move into the right position." Well, if there is a "right position" then there is a "wrong position" and what happens to the PC if they move into the wrong position? Would they not get stabbed by the assassin?
We don't know yet. I haven't written up the whole encounter area, or thought through what the assassin was prepared to do, like I would have in an actual game. It is a truism that if a creature is completely out of LOS of another creature, and the second creature moves into a position where the hidden creature is now completely revealed/in LOS of the moving creature, hey, presto, you can see him now! So I need the player to tell me where his character is moving. That way I can fairly rule on whether he now has clear LOS or doesn't.
This example seemed poor to me for a few reasons.
1) You don't need to roll athletics to climb a wall. To quote the PHB "Each foot of movement costs 1 extra foot (2 extra feet in difficult terrain) when you’re climbing, swimming, or crawling. You ignore this extra cost if you have a climbing speed and use it to climb, or a swimming speed and use it to swim. At the DM’s option, climbing a slippery vertical surface or one with few handholds requires a successful Strength (Athletics) check." So, only one of those walls could even be argued to need any check to climb. The wall with ivy is trivially climbable. The other was a brick wall, so again, trivially climbable, and only the last wall was smooth, which may require a check. Of course, that also depends on if the wall is higher than 15 ft, because at that point most parties have at least one character who can jump up and grab the top of the wall, pulling themselves up without a check and lowering a rope, which would not require a check to climb. You may even be able to reach higher if you have an ally boosting you. Which, again, would probably not require any check.
2) It was never clear to me if these were all walls facing the same direction, or different directions. If they are three walls facing three directions, then the player needs to declare which way they are going, but that has nothing to do with the walls. So it seemed to me that they had three different walls, all facing the same direction, and all leading to the same place. In which case, the only reason it matters which wall is if one of them is trapped. Which just leads to you playing Three-card monte with the players. If there are hazards on one of the walls and not the others, and I'm forcing the players to guess which wall is dangerous, for no discernible reason other than to hit the players who guess wrong with a trap.
This is again needlessly interpolating a hostile attitude.
@GMforPowergamers uses Athletics checks for climbing walls. He's made that clear. He's not exactly strict on the rules in the book.
The material point in the example was simply to illustrate that IF there is a hazard present in the scene, the DM needs some explanation from the characters about what elements of the scene their characters are interacting with, so we can tell whether the PCs have to deal with the hazard or just avoid it. And if there is NO hazard in the scene, skipping past players describing actions telegraphs to them that there was no hazard.
2) It was never clear to me if these were all walls facing the same direction, or different directions. If they are three walls facing three directions, then the player needs to declare which way they are going, but that has nothing to do with the walls. So it seemed to me that they had three different walls, all facing the same direction, and all leading to the same place. In which case, the only reason it matters which wall is if one of them is trapped. Which just leads to you playing Three-card monte with the players. If there are hazards on one of the walls and not the others, and I'm forcing the players to guess which wall is dangerous, for no discernible reason other than to hit the players who guess wrong with a trap.
It's not three card monte. I'm not cheating the players. Please stop that.
D&D has traps in it. D&D is a game in which the DM has secret information about those traps, and the players need to make smart decisions to avoid them. Or we can run them the naughty word way where they just pop up willy-nilly and inflict damage/force saves without PCs getting a chance to spot them or make smart decisions based on gathered information within the scenario to avoid them.
Maybe the whole palace garden grounds have that poisonous ivy in various spots. Maybe the PCs have opportunity to interrogate a gardener and find out about the ivy. Or to read the groundskeeper's notebook in his little office/maintenance building. Maybe the PCs can use that information to just avoid the ivy-covered walls, or maybe they stumble into them.
