I thought I knew, at first, how passive perception versus hidden/invisible creatures and/or well laid traps worked. I have a group of level 2 adventurers that are about to come upon their first trap after a few encounters where a few Wolf Spiders were able to easily sneak up on the group due their +7 Stealth and no one being perceptive enough to spot them, and no one making any perception checks to see if anything else was sneaking around.
Enter Quist, my new join who has no prior information on what unfolded so far in the campaign. Quist is a Human Variant Rogue with a Wisdom of 14 (+2) , proficiency with Perception (+2), the Observant Feat: (+5 Bonus to Passive Investigation AND Perception), and let's not forget the Rogues Expertise ability: double your proficiency bonus when making checks with two chosen proficient abilities or thieves tools.
So let's add that up. The math is 10 plus any bonuses to figure out Perception. 10 + 2 (wis) + 5 (Observant) + 4 Proficiency Bonus (Expert Perception doubles Proficiency bonus) = 21
So this Rogue is smashing through a DC check of 20 or lower against Stealth, Hide, Traps and the like PASSIVELY. What difficulty level is a DC 20 check? Hard. 25 Difficult and 30 Impossible. Did I do something wrong? I don't know when I began to lose control....or if I ever had it....but this Rogue just became my new God.
Now, my confusion begins when it comes to the research I tried to do on this matter. I found another question thread here that gave me a bit more insight into traps and such. If I have a trap with, say a DC of 15 to locate, what does that passive 21 actually show him? That something is amiss in that area and he still has to roll to locate the actual trap mechanics? Then he also has to roll to try and disarm it if he figures out how to do such? Or does the passive perception let him see the entire trap and it's workings? Secondly....I imagine only HE see's this trap, or the disturbed area of ground or whatever he may perceive to be wrong with the area, yes?
My follow up question is how does he Passive Perception effect Stealth/Hide abilities? Like if I wanted to set up an ambush of Dire Wolves with a Stealth of +4 . Some are visible, and I want to preemptively Stealth/Hide a few so that they're already hiding from the group when they come across them. What happens the moment good old observant Quist happens into the area and spots every single wolf, hidden or not?
I appreciate everyone's patience in dealing with my potential ignorance in this matter. I'm hoping my math is wrong but....it seems not to be. Right now Quist is sitting at a Passive Perception of 21 and a Passive Investigation of 22. How do I make that not game breaking; or throw them into EZ Mode :D