iserith
Magic Wordsmith
I would never use perception the way you do. Every player would move a small distance, stop, Observe, move small distance, stop Observe. It would drag the game too much. I do like the idea, but every intelligent creature in the world would do the same thing.
I'm not sure how you reached this conclusion based on what I wrote. This wouldn't be an outcome because that's, in part, what passive checks are for - resolving uncertain outcomes for tasks that are performed repeatedly. So, while traveling the dungeon, you're Keeping Watch for danger or whatever. Your passive Perception score applies whenever the DM determines surprise. If you're not Keeping Watch, then it doesn't apply and you're surprised if a monster is acting stealthily.
Nothing in any ruleset anyway require that PC be informed that you are in Initiative and thus Combat, that destroys any element of surprise.
"When a combat starts, every participant makes a Dexterity check to determine their place in the initiative order." Emphasis mine. By definition, when Initiative is rolled, everyone knows they're in a combat. The participants may or may not be surprised as determined by the DM.
If a enemy is hiding he is in combat, taking the hide action, and doing so over and over again waiting for the trigger. His initiative is set, its right before the PC who activates the trigger. Otherwise the PC can ruin an ambush just getting lucky on initiative, that's not the intent of the rules. An invisible, hidden behind total cover creature who rolled a 1 for initiative wont get the drop on anyone, the minute you call for initiative every PC knows something is there and all the PC will start taking actions to detect something that they should have no idea is there unless you say "you cant possibly detect anything so you cant take any actions" then makes the table feel screwed.
An enemy who is hiding is not necessarily in combat. The Hide action is something you can do in combat, given certain conditions, but a creature can also hide outside of combat by simply being unseen and unheard. Regardless, the scenario you're describing is covered by the rules for determining surprise. The invisible creature you mention meets the definition of one or both sides of the combat trying to be stealthy. So, the DM rolls a Dexterity (Stealth) check for the creature and, if that result is higher than a PC's passive Perception score (provided the PC was Keeping Watch and is in the position to notice the creature), then the PC is surprised unless he or she has the Alert feat or some other feature that negates surprise. Even if the surprised PC beats the invisible creature in initiative, the surprised PC does not get to take action before the invisible creature does, except for a reaction after the surprised PC's turn is passed.
If that's not an ambush, I don't know what is.
IMO, Passive Perception is misused by players and DMS alike. Here is the PHB example:
Use the passive Wisdom (Perception) scores of the characters to determine whether anyone in the group notices a hidden threat. The DM might decide that a threat can be noticed only by characters in a particular rank.
You cant ask your players their passive perception scores at the table, you give the game away then. You need to know them before the session starts, and then unless the PC tell you different like "We are moving slower to be aware of threats" they get no perception check to notice things, you only get your passive and only for the PC's in the right spots like in the example above. From Reddit user Ironforged:
Passive scores are a DM tool to use in two different situations.
The character is doing something over and over again repeatedly and you want to speed up play. Example, they are walking cautiously down a dungeon corridor on the lookout for traps and other dangers. You as the DM don't want to slow the game down by having them roll every ten or twenty feet, so you just use passive perception and passive investigation.
The character has a chance of doing something, but the act of rolling gives the player too much information so you want to test against their passive score so no roll is made. Example, when a group of monsters is about to ambush the party and surprise them, or when the succubus is disguise and blatantly lying to them, so you make the stealth and deception checks against passive perception and passive insight.
Those are the only two different ways covered in the PHB that passive scores are used.
The word "passive" has nothing to do with situation 1 at all but yet that is what they decided to call it, I think it wasn't the best term.
Addressing your concern, I don't ever have them roll if I used their passive score, it is either something I use to speed up play or to keep information from them, passive scores are not a safety net.
Also, passive perception still requires something for you to perceive. A silent creature hiding behind total cover that has no scent to me means no perception check will ever reveal them. That's what blind sight, tremor sense, etc are for.
I would say that the main misuse of passive Perception is treating it like it applies to resolving the outcome of all Perception-based tasks simultaneously. When taking the rules as a whole into account, it's clear to me that a player has to choose a single task and can't perform additional things that distract from that task. That immediately deals with objections to passive Perception being too powerful in my experience without making feats like Observant useless. It means you'll be good at whatever task you focus on, but not all Perception-related tasks at the same time. Only a ranger in favored terrain would be able to both Keep Watch and, say, search for secret doors simultaneously.
As for "giving away the game," I lay out the common tasks appropriate to the adventure location and the respective DCs when those outcomes are uncertain. The players can then establish their characters's tasks according to their strengths, weaknesses, and priorities. They can therefore decide that, for example, finding traps is really important to them, so they put their highest passive Perception character in the Front Rank (which might expose that character to greater risk). If the DC for finding secret doors at a slow pace is set to 15, they can put a PC with a passive Perception score of 10 in that task and have another PC work together with him or her to make it 15. Those characters will always be surprised, but they'll always find secret doors if they come across them - that's the risk they take for success. And so on. I then resolve outcomes as normal.