NOTE: Trusted friends told me my math was off. Hence the crossed off numbers. This is a work in progress.
Your character meets an NPC and you don’t trust them, not one bit. They are hiding something but you aren’t sure what. Roll the dice, then role-play a bit and step out of character to ask the DM questions as they occur to you or role-play through and ask the questions at the end.
DC 5 – a little detail, if you are going against a skilled liar and they rolled better than you, it might be something planted to lead you the wrong way. The DM can ask 1-2 questions to get information that the NPC has picked up about you.
10 7 – Ask the DM one question about the NPC you are evaluating but the DM may ask you a question because the NPC gets a read on you too.
15 12 – Ask the DM one question about the NPC you are evaluating.
20 17 – Ask the DM two questions about the NPC you are evaluating.
25 22 – Ask the DM three questions about the NPC you are evaluating.
30 27 – Ask the DM three questions about the NPC you are evaluating and they will tell you any remarkable statistics.
The questions should be things Sherlock Holmes could pick up about a suspect. The DM might ask you how you picked up such information from your interaction with the NPC; feel free to make up cool shit about how your character picked that up.
An opposed Deception roll can add to the DC and/or let the NPC pick up details on the character trying to learn about them. (NOTE: A trusted friend says this opposed roll will make this endeavor all but mathematically impossible. Noting this here while we discuss it).
From Matt Weber:
So, here’s the deal. By RAW, to make an Insight check against an NPC, you roll their Deception against the PC’s Insight. Many GMs will also just use the NPC’s Passive Deception, which is 10+(whatever their modifier is). Either way is valid, but that of course is using a binary pass / fail model, rather than your more interesting gradations.
If you have a set DC *and* the NPC gets to add their entire roll to that DC, that’s “double dipping” because fixed DCs are essentially supposed to replace a roll of the d20+(skill mod). Many NPCs don’t have much in the way of Deception, it’s true, but those that are trained in it could easily have +9 or higher.
UPDATE: Rather than a Perception vs. Insight roll…
If the villain has Deception, roll to see how ensconced they are in the area. Their Deception check is an optional roll to get an idea of how well their lies are covered. A good roll could get local NPC’s covering for them or insisting that their lie is truth, depending on the context. You don’t need to roll for this kind of thing but if you are building this situation on the fly, it can help give background.
When the dice hit the table, the status quo is going to be upended, tables will be flipped and secrets will be spilled.