The Skills section of Ability Scores portion of the PHB gives a rule for Passive Checks. This is usually only ever used with Perception; there’s even a special spot on every character sheet I’ve ever seen for passive Perception.
That doesn’t make a whole lot of sense to me. If Perception can have a passive score, why not Insight? Why not Nature?
After all, what we classify as knowledge is senses and neurons firing away. When you see a dog, you don’t roll Nature to figure out it’s a dog; your brain simply provides the information. If you see a hyena, your brain remembers the National Geographic episode you watched ten years ago that featured that African something which resembles a dog, and had a weird bark like a laugh, oh yeah, a hyena.
I’ve been making things move at my table more easily by making passive uses of skills automatic. Skills were turning into a game within a game, a game of asking questions until they ask the right one which lets them make a skill check.
Under this principle, all skills are assumed to represent both active uses of the skills and relevant background knowledge, lore, information, and awareness. When a character with proficiency in a skill encounters something in the game, I simply give them any relevant information based on that expertise. I filter how much information I give based on skill-proficiency “DCs.” Advanced knowledge and specific knowledge is still dependent on a skill-check die roll to simulate actively using that proficiency.
I’m going to start putting that into the adventures I write and sell through the DMs Guild, too. Descriptive flavor text will be written with cues for passive skill scores. Like this:
You enter an ornately-carved chamber, featuring statues of dwarf deities. There is a dais at the far end of the chamber on which stands a stone altar inscribed with a stylized hammer and runes.
[Religion] The runes praise Berronar Truesilver.
[Religion 14] The altar was used by priests to bless and heal.
[Religion 18] If a creature spends a short rest meditating within 10 feet of the altar, that creature adds +2 to each hit die they spend to regain hit points during that rest.
That’s just one example. It really speeds up exploration, though it can reduce player engagement. But since player engagement in this instance is based on die rolls which often make little sense, it works. For example, by the RAW, if a character proficient in Religion examined the altar, they might roll a 2. It’s pretty stupid that they suddenly remember nothing. If their passive Religion was 15, they’d not get the Religion 18 entry (which they would have had they rolled a d20 score totaling 18 or more), but they would get the Religion 14 information without even trying. This simulates those times when you rack your brain trying to remember something but only succeed in driving it farther from your conscious mind.
Of course you should remind that character an hour later about that information, just to rub it in. “Oh, Durin? You just remembered something interesting about that altar…”
This is going in the new edition of You Can Try: Tips on Becoming a Better DM.